Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Aaron Levinson]

On 5/12/2017 5:51 PM, Michael Niedermayer wrote:

On Fri, May 12, 2017 at 01:19:43PM -0700, Aaron Levinson wrote:

On 5/9/2017 11:56 AM, Michael Niedermayer wrote:

On Thu, May 04, 2017 at 11:46:30PM -0700, Aaron Levinson wrote:


I've provided a new version of the patch.  When I created the first version of the patch on March 
26th, this was the first patch that I submitted to ffmpeg, and some aspects were rough.  I had 
indicated that the patch passed regression tests, but all I did was run "make fate", 
instead of "make fate SAMPLES=fate-suite/", and once I understood that I should use 
fate-suite, I discovered that some of the FATE tests failed with this patch.  I fixed the issues 
with the patch, adjusted some comments, and adjusted the patch description text.  I've confirmed 
that this patch passes all fate-suite tests for 64-bit MSVC on Windows and 64-bit gcc on Linux.

Thanks,
Aaron Levinson




>From 85aa383f5753795652bae015f4fe91b016f7387e Mon Sep 17 00:00:00 2001

From: Aaron Levinson 
Date: Thu, 4 May 2017 22:54:31 -0700
Subject: [PATCH] ffmpeg:  Fixed bug with decoding interlaced video

Purpose: Fixed bug in ffmpeg encountered when decoding interlaced
video.  In some cases, ffmpeg would treat it as progressive.  As a
result of the change, the issues with interlaced video are fixed.

Detailed description of problem: Run the following command: "ffmpeg -i
test8_1080i.h264 -c:v mpeg2video test8_1080i_mp2.ts".  In this case,
test8_1080i.h264 is an H.264-encoded file with 1080i59.94
(interlaced).  Prior to the patch, the following output is generated:

Input #0, h264, from 'test8_1080i.h264':
 Duration: N/A, bitrate: N/A
   Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 
16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
Stream mapping:
 Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
Press [q] to stop, [?] for help
Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
 Metadata:
   encoder : Lavf57.72.100
   Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR 
16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
   Metadata:
 encoder : Lavc57.92.100 mpeg2video

which demonstrates the bug.  The output should instead look like:

   Stream #0:0: Video: mpeg2video (Main), yuv420p(top coded first (swapped)), 
1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc

The bug is caused by the fact that reap_filters() calls
init_output_stream(), which in turn calls check_init_output_file(),
and this is all done prior to the first call to do_video_out().  An
initial call to do_video_out() is necessary to populate the interlaced
video information to the output stream's codecpar
(mux_par->field_order in do_video_out()).  However,
check_init_output_file() calls avformat_write_header() prior to the
initial call to do_video_out(), so field_order is populated too late,
and the header is written with the default field_order value,
progressive.

Comments:

-- ffmpeg.c:
a) Enhanced init_output_stream() to take an additional input
  indicating whether or not check_init_output_file() should be
  called.  There are other places that call init_output_stream(), and
  it was important to make sure that these continued to work
  properly.
b) Adjusted reap_filters() such that, in the case that
  init_output_stream() is called, it indicates that it should not
  call check_init_output_file() in init_output_stream().  Instead, it
  makes the call to check_init_output_file() directly, but after it
  does the filtered frame setup and processing.

Signed-off-by: Aaron Levinson 
---
ffmpeg.c | 61 +
1 file changed, 53 insertions(+), 8 deletions(-)

diff --git a/ffmpeg.c b/ffmpeg.c
index e798d92277..45dbfafc04 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c



@@ -1400,7 +1400,7 @@ static void do_video_stats(OutputStream *ost, int 
frame_size)
}
}

-static int init_output_stream(OutputStream *ost, char *error, int error_len);
+static int init_output_stream(OutputStream *ost, char *error, int error_len, 
int do_check_output_file);

static void finish_output_stream(OutputStream *ost)
{



@@ -1415,6 +1415,8 @@ static void finish_output_stream(OutputStream *ost)
}
}

+static int check_init_output_file(OutputFile *of, int file_index);


should be close to the file top, together with similar prototypes


Will do.


[...]

@@ -1521,6 +1526,44 @@ static int reap_filters(int flush)
}

av_frame_unref(filtered_frame);
+
+/*
+ * It is important to call check_init_output_file() here, after
+ * do_video_out() was called, instead of in init_output_stream(),
+ * as was done previously.
+ * If called from init_output_stream(), it is possible that not
+ * everything will have been fully 

Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Michael Niedermayer]

On Fri, May 12, 2017 at 01:19:43PM -0700, Aaron Levinson wrote:
> On 5/9/2017 11:56 AM, Michael Niedermayer wrote:
> >On Thu, May 04, 2017 at 11:46:30PM -0700, Aaron Levinson wrote:
> >>
> >>I've provided a new version of the patch.  When I created the first version 
> >>of the patch on March 26th, this was the first patch that I submitted to 
> >>ffmpeg, and some aspects were rough.  I had indicated that the patch passed 
> >>regression tests, but all I did was run "make fate", instead of "make fate 
> >>SAMPLES=fate-suite/", and once I understood that I should use fate-suite, I 
> >>discovered that some of the FATE tests failed with this patch.  I fixed the 
> >>issues with the patch, adjusted some comments, and adjusted the patch 
> >>description text.  I've confirmed that this patch passes all fate-suite 
> >>tests for 64-bit MSVC on Windows and 64-bit gcc on Linux.
> >>
> >>Thanks,
> >>Aaron Levinson
> >>
> >>
> >>
> >>From 85aa383f5753795652bae015f4fe91b016f7387e Mon Sep 17 00:00:00 2001
> >>From: Aaron Levinson 
> >>Date: Thu, 4 May 2017 22:54:31 -0700
> >>Subject: [PATCH] ffmpeg:  Fixed bug with decoding interlaced video
> >>
> >>Purpose: Fixed bug in ffmpeg encountered when decoding interlaced
> >>video.  In some cases, ffmpeg would treat it as progressive.  As a
> >>result of the change, the issues with interlaced video are fixed.
> >>
> >>Detailed description of problem: Run the following command: "ffmpeg -i
> >>test8_1080i.h264 -c:v mpeg2video test8_1080i_mp2.ts".  In this case,
> >>test8_1080i.h264 is an H.264-encoded file with 1080i59.94
> >>(interlaced).  Prior to the patch, the following output is generated:
> >>
> >>Input #0, h264, from 'test8_1080i.h264':
> >>  Duration: N/A, bitrate: N/A
> >>Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 
> >> DAR 16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
> >>Stream mapping:
> >>  Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
> >>Press [q] to stop, [?] for help
> >>Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
> >>  Metadata:
> >>encoder : Lavf57.72.100
> >>Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR 
> >> 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
> >>Metadata:
> >>  encoder : Lavc57.92.100 mpeg2video
> >>
> >>which demonstrates the bug.  The output should instead look like:
> >>
> >>Stream #0:0: Video: mpeg2video (Main), yuv420p(top coded first 
> >> (swapped)), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k 
> >> tbn, 29.97 tbc
> >>
> >>The bug is caused by the fact that reap_filters() calls
> >>init_output_stream(), which in turn calls check_init_output_file(),
> >>and this is all done prior to the first call to do_video_out().  An
> >>initial call to do_video_out() is necessary to populate the interlaced
> >>video information to the output stream's codecpar
> >>(mux_par->field_order in do_video_out()).  However,
> >>check_init_output_file() calls avformat_write_header() prior to the
> >>initial call to do_video_out(), so field_order is populated too late,
> >>and the header is written with the default field_order value,
> >>progressive.
> >>
> >>Comments:
> >>
> >>-- ffmpeg.c:
> >>a) Enhanced init_output_stream() to take an additional input
> >>   indicating whether or not check_init_output_file() should be
> >>   called.  There are other places that call init_output_stream(), and
> >>   it was important to make sure that these continued to work
> >>   properly.
> >>b) Adjusted reap_filters() such that, in the case that
> >>   init_output_stream() is called, it indicates that it should not
> >>   call check_init_output_file() in init_output_stream().  Instead, it
> >>   makes the call to check_init_output_file() directly, but after it
> >>   does the filtered frame setup and processing.
> >>
> >>Signed-off-by: Aaron Levinson 
> >>---
> >> ffmpeg.c | 61 +
> >> 1 file changed, 53 insertions(+), 8 deletions(-)
> >>
> >>diff --git a/ffmpeg.c b/ffmpeg.c
> >>index e798d92277..45dbfafc04 100644
> >>--- a/ffmpeg.c
> >>+++ b/ffmpeg.c
> >
> >>@@ -1400,7 +1400,7 @@ static void do_video_stats(OutputStream *ost, int 
> >>frame_size)
> >> }
> >> }
> >>
> >>-static int init_output_stream(OutputStream *ost, char *error, int 
> >>error_len);
> >>+static int init_output_stream(OutputStream *ost, char *error, int 
> >>error_len, int do_check_output_file);
> >>
> >> static void finish_output_stream(OutputStream *ost)
> >> {
> >
> >>@@ -1415,6 +1415,8 @@ static void finish_output_stream(OutputStream *ost)
> >> }
> >> }
> >>
> >>+static int check_init_output_file(OutputFile *of, int file_index);
> >
> >should be close to the file top, together with similar prototypes
> 
> Will do.
> 
> >[...]
> >>@@ -1521,6 +1526,44 @@ static int reap_filters(int 

Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Aaron Levinson]

On 5/9/2017 11:56 AM, Michael Niedermayer wrote:

On Thu, May 04, 2017 at 11:46:30PM -0700, Aaron Levinson wrote:


I've provided a new version of the patch.  When I created the first version of the patch on March 
26th, this was the first patch that I submitted to ffmpeg, and some aspects were rough.  I had 
indicated that the patch passed regression tests, but all I did was run "make fate", 
instead of "make fate SAMPLES=fate-suite/", and once I understood that I should use 
fate-suite, I discovered that some of the FATE tests failed with this patch.  I fixed the issues 
with the patch, adjusted some comments, and adjusted the patch description text.  I've confirmed 
that this patch passes all fate-suite tests for 64-bit MSVC on Windows and 64-bit gcc on Linux.

Thanks,
Aaron Levinson



From 85aa383f5753795652bae015f4fe91b016f7387e Mon Sep 17 00:00:00 2001
From: Aaron Levinson 
Date: Thu, 4 May 2017 22:54:31 -0700
Subject: [PATCH] ffmpeg:  Fixed bug with decoding interlaced video

Purpose: Fixed bug in ffmpeg encountered when decoding interlaced
video.  In some cases, ffmpeg would treat it as progressive.  As a
result of the change, the issues with interlaced video are fixed.

Detailed description of problem: Run the following command: "ffmpeg -i
test8_1080i.h264 -c:v mpeg2video test8_1080i_mp2.ts".  In this case,
test8_1080i.h264 is an H.264-encoded file with 1080i59.94
(interlaced).  Prior to the patch, the following output is generated:

Input #0, h264, from 'test8_1080i.h264':
  Duration: N/A, bitrate: N/A
Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 
16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
Press [q] to stop, [?] for help
Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
  Metadata:
encoder : Lavf57.72.100
Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR 
16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
Metadata:
  encoder : Lavc57.92.100 mpeg2video

which demonstrates the bug.  The output should instead look like:

Stream #0:0: Video: mpeg2video (Main), yuv420p(top coded first (swapped)), 
1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc

The bug is caused by the fact that reap_filters() calls
init_output_stream(), which in turn calls check_init_output_file(),
and this is all done prior to the first call to do_video_out().  An
initial call to do_video_out() is necessary to populate the interlaced
video information to the output stream's codecpar
(mux_par->field_order in do_video_out()).  However,
check_init_output_file() calls avformat_write_header() prior to the
initial call to do_video_out(), so field_order is populated too late,
and the header is written with the default field_order value,
progressive.

Comments:

-- ffmpeg.c:
a) Enhanced init_output_stream() to take an additional input
   indicating whether or not check_init_output_file() should be
   called.  There are other places that call init_output_stream(), and
   it was important to make sure that these continued to work
   properly.
b) Adjusted reap_filters() such that, in the case that
   init_output_stream() is called, it indicates that it should not
   call check_init_output_file() in init_output_stream().  Instead, it
   makes the call to check_init_output_file() directly, but after it
   does the filtered frame setup and processing.

Signed-off-by: Aaron Levinson 
---
 ffmpeg.c | 61 +
 1 file changed, 53 insertions(+), 8 deletions(-)

diff --git a/ffmpeg.c b/ffmpeg.c
index e798d92277..45dbfafc04 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c



@@ -1400,7 +1400,7 @@ static void do_video_stats(OutputStream *ost, int 
frame_size)
 }
 }

-static int init_output_stream(OutputStream *ost, char *error, int error_len);
+static int init_output_stream(OutputStream *ost, char *error, int error_len, 
int do_check_output_file);

 static void finish_output_stream(OutputStream *ost)
 {



@@ -1415,6 +1415,8 @@ static void finish_output_stream(OutputStream *ost)
 }
 }

+static int check_init_output_file(OutputFile *of, int file_index);


should be close to the file top, together with similar prototypes


Will do.


[...]

@@ -1521,6 +1526,44 @@ static int reap_filters(int flush)
 }

 av_frame_unref(filtered_frame);
+
+/*
+ * It is important to call check_init_output_file() here, after
+ * do_video_out() was called, instead of in init_output_stream(),
+ * as was done previously.
+ * If called from init_output_stream(), it is possible that not
+ * everything will have been fully initialized by the time that
+ * check_init_output_file() is called, and if
+

Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Michael Niedermayer]

On Thu, May 04, 2017 at 11:46:30PM -0700, Aaron Levinson wrote:
> On 4/12/2017 6:08 PM, Aaron Levinson wrote:
> > On 3/26/2017 10:34 AM, Aaron Levinson wrote:
> >> On 3/26/2017 4:41 AM, Matthias Hunstock wrote:
> >>> Am 26.03.2017 um 11:50 schrieb Aaron Levinson:
>  When using the following command to play back either file:
>   ffmpeg -i  -f decklink -pix_fmt uyvy422 "DeckLink SDI
>   4K", I noticed that with the mpegts file with the AAC audio stream,
>   it would correctly select an interlaced video mode for the video
>   output stream, but with the mpegts file with the Opus audio stream,
>   it would use a progressive video mode (1080p29.97) for the video
>   output stream.
> >>>
> >>> Which FFmpeg version did you test this with?
> >>>
> >>> There was a change related to this just short time ago.
> >>>
> >>> Does it happen with current git HEAD?
> >>>
> >>> Matthias
> >>
> >> This issue occurs with the current git HEAD.  I'm aware of the
> >> Blackmagic improvement that was added in February to add support for
> >> interlaced video modes on output, and actually that's one of the reasons
> >> why I'm using the latest git sources, as opposed to, say, 3.2.4.  This
> >> particular issue has nothing to do with Blackmagic, and I only used
> >> Blackmagic in the example that reproduces the bug because it is
> >> something that can be reproduced on both Windows and Linux (and
> >> presumably also on OS/X).  The issue also occurs if I do something like
> >> -f rawvideo out.avi on Windows, and I'm sure that there are plenty of
> >> other examples.
> >>
> >> Aaron Levinson
> > 
> > Has anyone had a chance to review this patch yet, which I submitted on 
> > March 26th?  To demonstrate the impact of this patch, here's some output of 
> > before and after for an .h264 file with interlaced 1080i59.94 video content:
> > 
> > Command-line:  ffmpeg -i test8_1080i.h264 -c:v mpeg2video test8_1080i_mp2.ts
> > 
> > Before patch:
> > 
> > --
> > 
> > Input #0, h264, from 'test8_1080i.h264':
> >   Duration: N/A, bitrate: N/A
> > Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 
> > DAR 16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
> > Stream mapping:
> >   Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
> > Press [q] to stop, [?] for help
> > Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
> >   Metadata:
> > encoder : Lavf57.72.100
> > Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR 
> > 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
> > Metadata:
> >   encoder : Lavc57.92.100 mpeg2video
> > Side data:
> >   cpb: bitrate max/min/avg: 0/0/20 buffer size: 0 vbv_delay: -1
> > 
> > --
> > 
> > After patch:
> > 
> > --
> > 
> > Input #0, h264, from 'test8_1080i.h264':
> >   Duration: N/A, bitrate: N/A
> > Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 
> > DAR 16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
> > Stream mapping:
> >   Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
> > Press [q] to stop, [?] for help
> > Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
> >   Metadata:
> > encoder : Lavf57.72.100
> > Stream #0:0: Video: mpeg2video (Main), yuv420p(top coded first 
> > (swapped)), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k 
> > tbn, 29.97 tbc
> > Metadata:
> >   encoder : Lavc57.92.100 mpeg2video
> > Side data:
> >   cpb: bitrate max/min/avg: 0/0/20 buffer size: 0 vbv_delay: -1
> > 
> > --
> > 
> > As can be seen, before the patch, after decoding the .h264 file and then 
> > re-encoding it as mpeg2video in an mpegts container, the interlaced aspect 
> > of the video has been lost in the output, and it is now effectively 
> > 1080p29.97, although the video hasn't actually been converted to 
> > progressive.  ffmpeg simply thinks that the video is progressive when it is 
> > not.  With the patch, the interlaced aspect is not lost and propagates to 
> > the output.  So, this conclusively demonstrates that the issue has nothing 
> > to do with Blackmagic and is a more general issue with interlaced video and 
> > decoding.
> > 
> > I can make the input file available if that would be helpful.
> > 
> > Anyway, it would be great if this bug fix could make it into ffmpeg.
> > 
> > Thanks,
> > Aaron Levinson
> 
> I've provided a new version of the patch.  When I created the first version 
> of the patch on March 26th, this was the first patch that I submitted to 
> ffmpeg, and some aspects were rough.  I had indicated that the patch passed 
> regression tests, but all I did was run "make fate", instead of "make fate 
> SAMPLES=fate-suite/", and once I understood that I should use fate-suite, I 
> discovered that some of the FATE tests failed 

Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Aaron Levinson]

On 5/5/2017 2:26 AM, wm4 wrote:

On Fri, 5 May 2017 01:11:17 -0700
Aaron Levinson  wrote:


As I said on IRC, I'm skeptic against this, but I'm also not sure
whether I understand the situation.

First, your change seems a bit fragile, and almost relies on
coincidences. This could easily break in the future. (And if we add a
FATE test, it would probably hit random people trying to change
ffmpeg.c, and would cause them more work.)


I guess I don't understand why you think this change is fragile, relies
on coincidences, and could easily break in the future.


Well, the implemented and working logic is that ffmpeg.c waits until it
has encoded packets for every stream, and then writes the file headers.
That should work pretty well to let metadata naturally "flow" through
decoder, filters, and encoder. But your case doesn't fit right into it,
so you apparently have to make it somehow call do_video_out() more.
(Also a thing I don't understand - do_video_out() should have been
called at least once to encode a video packet.)


That's not how ffmpeg.c behaves today.  It writes the file headers 
before it has any encoded packets for the _last_ output stream that is 
initialized.  With my change, I make sure that the file headers aren't 
written until after it has had an opportunity to generate encoded 
packets for at least one input frame for all output streams, although 
there are some FATE test cases in which input frames aren't ready yet by 
this point, which explains why the existence of the fallback in my patch 
is necessary.


It doesn't call do_video_out() any more times with my patch than prior 
to my patch.  It just changes the order of when check_init_output_file() 
is called with respect to do_video_out() (and do_audio_out()).



And looking at how field_order is set, the existing code doesn't make
sense in the first place.

So maybe it would be better to fix the actual problem, instead of
adding another workaround.

At least that's my thinking.


 The existing
code is already fragile.


Indeed. That (and me being sleep deprived) probably contributes to that
I just don't understand your fix.

Also feel free to ignore me - I'm neither maintainer of ffmpeg.c nor an
authority on it.


 As I indicated in previous e-mails on this
topic, the behavior of the current code can change depending on timing
when there is more than one stream.  This patch should make things more
deterministic.  And, I do think it is appropriate to add an interlaced
video decoding FATE test, although there is no point to doing so until
this bug is fixed, as the current behavior is broken.


Looking at the current do_video_out() function (which btw. is way too
long and also has broken indentation), I see the following line:

  mux_par->field_order = AV_FIELD_PROGRESSIVE;

(and similar assignments to field_order to set interlaced modes)

This is apparently run on every frame. This looks pretty wrong to me.
It should _never_ change the codecpar after headers were written. This
is simply invalid API use.

If this is really a parameter that can change per frame, and that the
_muxer_ needs this information (per packet I suppose), a side data
signaling the field order should be added. mpegtsenc.c doesn't seem to
read field_order at all, though.

So I remain confused.


Yes, I agree that the approach of changing field_order for every frame
is not the right way to go, but this code was already existing.  A
future patch could undertake the task of handling interlaced video in a
more proper way, and I wrote a TODO comment to that point.


I don't understand that comment either. As I already said,
do_video_out() has to be _necessarily_ called before the muxer can be
initialized (aka writing headers).


The way the code is currently structured, do_video_out() is called by 
reap_filters() after it calls init_output_stream(), and it is 
init_output_stream() that makes the call to check_init_output_file(), 
which is where the call to avformat_write_header() is done. 
reap_filters() is the only function that calls do_video_out(), and I 
think it is pretty clear that this will be done after it calls 
init_output_stream() from looking at the source code.


My TODO has to do with setting up the field order based on header 
information, rather than waiting till it gets the first input frame. 
That's the theory at least, but I don't currently know how to do that in 
practice within ffmpeg.c.


Aaron Levinson
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Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[wm4]

On Fri, 5 May 2017 01:11:17 -0700
Aaron Levinson  wrote:

> > As I said on IRC, I'm skeptic against this, but I'm also not sure
> > whether I understand the situation.
> >
> > First, your change seems a bit fragile, and almost relies on
> > coincidences. This could easily break in the future. (And if we add a
> > FATE test, it would probably hit random people trying to change
> > ffmpeg.c, and would cause them more work.)  
> 
> I guess I don't understand why you think this change is fragile, relies 
> on coincidences, and could easily break in the future.

Well, the implemented and working logic is that ffmpeg.c waits until it
has encoded packets for every stream, and then writes the file headers.
That should work pretty well to let metadata naturally "flow" through
decoder, filters, and encoder. But your case doesn't fit right into it,
so you apparently have to make it somehow call do_video_out() more.
(Also a thing I don't understand - do_video_out() should have been
called at least once to encode a video packet.)

And looking at how field_order is set, the existing code doesn't make
sense in the first place.

So maybe it would be better to fix the actual problem, instead of
adding another workaround.

At least that's my thinking.

>  The existing 
> code is already fragile.

Indeed. That (and me being sleep deprived) probably contributes to that
I just don't understand your fix.

Also feel free to ignore me - I'm neither maintainer of ffmpeg.c nor an
authority on it.

>  As I indicated in previous e-mails on this 
> topic, the behavior of the current code can change depending on timing 
> when there is more than one stream.  This patch should make things more 
> deterministic.  And, I do think it is appropriate to add an interlaced 
> video decoding FATE test, although there is no point to doing so until 
> this bug is fixed, as the current behavior is broken.
> 
> > Looking at the current do_video_out() function (which btw. is way too
> > long and also has broken indentation), I see the following line:
> >
> >   mux_par->field_order = AV_FIELD_PROGRESSIVE;
> >
> > (and similar assignments to field_order to set interlaced modes)
> >
> > This is apparently run on every frame. This looks pretty wrong to me.
> > It should _never_ change the codecpar after headers were written. This
> > is simply invalid API use.
> >
> > If this is really a parameter that can change per frame, and that the
> > _muxer_ needs this information (per packet I suppose), a side data
> > signaling the field order should be added. mpegtsenc.c doesn't seem to
> > read field_order at all, though.
> >
> > So I remain confused.  
> 
> Yes, I agree that the approach of changing field_order for every frame 
> is not the right way to go, but this code was already existing.  A 
> future patch could undertake the task of handling interlaced video in a 
> more proper way, and I wrote a TODO comment to that point.

I don't understand that comment either. As I already said,
do_video_out() has to be _necessarily_ called before the muxer can be
initialized (aka writing headers).
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Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Aaron Levinson]

On 5/5/2017 12:55 AM, wm4 wrote:

On Thu, 4 May 2017 23:46:30 -0700
Aaron Levinson  wrote:


On 4/12/2017 6:08 PM, Aaron Levinson wrote:

On 3/26/2017 10:34 AM, Aaron Levinson wrote:

On 3/26/2017 4:41 AM, Matthias Hunstock wrote:

Am 26.03.2017 um 11:50 schrieb Aaron Levinson:

> [...]
>>> [...]

I've provided a new version of the patch.  When I created the first version of the patch on March 
26th, this was the first patch that I submitted to ffmpeg, and some aspects were rough.  I had 
indicated that the patch passed regression tests, but all I did was run "make fate", 
instead of "make fate SAMPLES=fate-suite/", and once I understood that I should use 
fate-suite, I discovered that some of the FATE tests failed with this patch.  I fixed the issues 
with the patch, adjusted some comments, and adjusted the patch description text.  I've confirmed 
that this patch passes all fate-suite tests for 64-bit MSVC on Windows and 64-bit gcc on Linux.

Thanks,
Aaron Levinson



From 85aa383f5753795652bae015f4fe91b016f7387e Mon Sep 17 00:00:00 2001
From: Aaron Levinson 
Date: Thu, 4 May 2017 22:54:31 -0700
Subject: [PATCH] ffmpeg:  Fixed bug with decoding interlaced video

Purpose: Fixed bug in ffmpeg encountered when decoding interlaced
video.  In some cases, ffmpeg would treat it as progressive.  As a
result of the change, the issues with interlaced video are fixed.

Detailed description of problem: Run the following command: "ffmpeg -i
test8_1080i.h264 -c:v mpeg2video test8_1080i_mp2.ts".  In this case,
test8_1080i.h264 is an H.264-encoded file with 1080i59.94
(interlaced).  Prior to the patch, the following output is generated:

Input #0, h264, from 'test8_1080i.h264':
  Duration: N/A, bitrate: N/A
Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 
16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
Press [q] to stop, [?] for help
Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
  Metadata:
encoder : Lavf57.72.100
Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR 
16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
Metadata:
  encoder : Lavc57.92.100 mpeg2video

which demonstrates the bug.  The output should instead look like:

Stream #0:0: Video: mpeg2video (Main), yuv420p(top coded first (swapped)), 
1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc

The bug is caused by the fact that reap_filters() calls
init_output_stream(), which in turn calls check_init_output_file(),
and this is all done prior to the first call to do_video_out().  An
initial call to do_video_out() is necessary to populate the interlaced
video information to the output stream's codecpar
(mux_par->field_order in do_video_out()).  However,
check_init_output_file() calls avformat_write_header() prior to the
initial call to do_video_out(), so field_order is populated too late,
and the header is written with the default field_order value,
progressive.

Comments:

-- ffmpeg.c:
a) Enhanced init_output_stream() to take an additional input
   indicating whether or not check_init_output_file() should be
   called.  There are other places that call init_output_stream(), and
   it was important to make sure that these continued to work
   properly.
b) Adjusted reap_filters() such that, in the case that
   init_output_stream() is called, it indicates that it should not
   call check_init_output_file() in init_output_stream().  Instead, it
   makes the call to check_init_output_file() directly, but after it
   does the filtered frame setup and processing.

Signed-off-by: Aaron Levinson 
---
 ffmpeg.c | 61 +
 1 file changed, 53 insertions(+), 8 deletions(-)

diff --git a/ffmpeg.c b/ffmpeg.c
index e798d92277..45dbfafc04 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c
@@ -1400,7 +1400,7 @@ static void do_video_stats(OutputStream *ost, int 
frame_size)
 }
 }

-static int init_output_stream(OutputStream *ost, char *error, int error_len);
+static int init_output_stream(OutputStream *ost, char *error, int error_len, 
int do_check_output_file);

 static void finish_output_stream(OutputStream *ost)
 {
@@ -1415,6 +1415,8 @@ static void finish_output_stream(OutputStream *ost)
 }
 }

+static int check_init_output_file(OutputFile *of, int file_index);
+
 /**
  * Get and encode new output from any of the filtergraphs, without causing
  * activity.
@@ -1433,6 +1435,7 @@ static int reap_filters(int flush)
 AVFilterContext *filter;
 AVCodecContext *enc = ost->enc_ctx;
 int ret = 0;
+int did_init_output_stream = 0;

 if (!ost->filter || !ost->filter->graph->graph)
 continue;
@@ -1440,12 +1443,14 @@ static int reap_filters(int flush)

   

Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[wm4]

On Thu, 4 May 2017 23:46:30 -0700
Aaron Levinson  wrote:

> On 4/12/2017 6:08 PM, Aaron Levinson wrote:
> > On 3/26/2017 10:34 AM, Aaron Levinson wrote:  
> >> On 3/26/2017 4:41 AM, Matthias Hunstock wrote:  
> >>> Am 26.03.2017 um 11:50 schrieb Aaron Levinson:  
>  When using the following command to play back either file:
>   ffmpeg -i  -f decklink -pix_fmt uyvy422 "DeckLink SDI
>   4K", I noticed that with the mpegts file with the AAC audio stream,
>   it would correctly select an interlaced video mode for the video
>   output stream, but with the mpegts file with the Opus audio stream,
>   it would use a progressive video mode (1080p29.97) for the video
>   output stream.  
> >>>
> >>> Which FFmpeg version did you test this with?
> >>>
> >>> There was a change related to this just short time ago.
> >>>
> >>> Does it happen with current git HEAD?
> >>>
> >>> Matthias  
> >>
> >> This issue occurs with the current git HEAD.  I'm aware of the
> >> Blackmagic improvement that was added in February to add support for
> >> interlaced video modes on output, and actually that's one of the reasons
> >> why I'm using the latest git sources, as opposed to, say, 3.2.4.  This
> >> particular issue has nothing to do with Blackmagic, and I only used
> >> Blackmagic in the example that reproduces the bug because it is
> >> something that can be reproduced on both Windows and Linux (and
> >> presumably also on OS/X).  The issue also occurs if I do something like
> >> -f rawvideo out.avi on Windows, and I'm sure that there are plenty of
> >> other examples.
> >>
> >> Aaron Levinson  
> > 
> > Has anyone had a chance to review this patch yet, which I submitted on 
> > March 26th?  To demonstrate the impact of this patch, here's some output of 
> > before and after for an .h264 file with interlaced 1080i59.94 video content:
> > 
> > Command-line:  ffmpeg -i test8_1080i.h264 -c:v mpeg2video test8_1080i_mp2.ts
> > 
> > Before patch:
> > 
> > --
> > 
> > Input #0, h264, from 'test8_1080i.h264':
> >   Duration: N/A, bitrate: N/A
> > Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 
> > DAR 16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
> > Stream mapping:
> >   Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
> > Press [q] to stop, [?] for help
> > Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
> >   Metadata:
> > encoder : Lavf57.72.100
> > Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR 
> > 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
> > Metadata:
> >   encoder : Lavc57.92.100 mpeg2video
> > Side data:
> >   cpb: bitrate max/min/avg: 0/0/20 buffer size: 0 vbv_delay: -1
> > 
> > --
> > 
> > After patch:
> > 
> > --
> > 
> > Input #0, h264, from 'test8_1080i.h264':
> >   Duration: N/A, bitrate: N/A
> > Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 
> > DAR 16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
> > Stream mapping:
> >   Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
> > Press [q] to stop, [?] for help
> > Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
> >   Metadata:
> > encoder : Lavf57.72.100
> > Stream #0:0: Video: mpeg2video (Main), yuv420p(top coded first 
> > (swapped)), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k 
> > tbn, 29.97 tbc
> > Metadata:
> >   encoder : Lavc57.92.100 mpeg2video
> > Side data:
> >   cpb: bitrate max/min/avg: 0/0/20 buffer size: 0 vbv_delay: -1
> > 
> > --
> > 
> > As can be seen, before the patch, after decoding the .h264 file and then 
> > re-encoding it as mpeg2video in an mpegts container, the interlaced aspect 
> > of the video has been lost in the output, and it is now effectively 
> > 1080p29.97, although the video hasn't actually been converted to 
> > progressive.  ffmpeg simply thinks that the video is progressive when it is 
> > not.  With the patch, the interlaced aspect is not lost and propagates to 
> > the output.  So, this conclusively demonstrates that the issue has nothing 
> > to do with Blackmagic and is a more general issue with interlaced video and 
> > decoding.
> > 
> > I can make the input file available if that would be helpful.
> > 
> > Anyway, it would be great if this bug fix could make it into ffmpeg.
> > 
> > Thanks,
> > Aaron Levinson  
> 
> I've provided a new version of the patch.  When I created the first version 
> of the patch on March 26th, this was the first patch that I submitted to 
> ffmpeg, and some aspects were rough.  I had indicated that the patch passed 
> regression tests, but all I did was run "make fate", instead of "make fate 
> SAMPLES=fate-suite/", and once I understood that I should use fate-suite, I 
> discovered that 

Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Aaron Levinson]

On 4/12/2017 6:08 PM, Aaron Levinson wrote:
> On 3/26/2017 10:34 AM, Aaron Levinson wrote:
>> On 3/26/2017 4:41 AM, Matthias Hunstock wrote:
>>> Am 26.03.2017 um 11:50 schrieb Aaron Levinson:
 When using the following command to play back either file:
  ffmpeg -i  -f decklink -pix_fmt uyvy422 "DeckLink SDI
  4K", I noticed that with the mpegts file with the AAC audio stream,
  it would correctly select an interlaced video mode for the video
  output stream, but with the mpegts file with the Opus audio stream,
  it would use a progressive video mode (1080p29.97) for the video
  output stream.
>>>
>>> Which FFmpeg version did you test this with?
>>>
>>> There was a change related to this just short time ago.
>>>
>>> Does it happen with current git HEAD?
>>>
>>> Matthias
>>
>> This issue occurs with the current git HEAD.  I'm aware of the
>> Blackmagic improvement that was added in February to add support for
>> interlaced video modes on output, and actually that's one of the reasons
>> why I'm using the latest git sources, as opposed to, say, 3.2.4.  This
>> particular issue has nothing to do with Blackmagic, and I only used
>> Blackmagic in the example that reproduces the bug because it is
>> something that can be reproduced on both Windows and Linux (and
>> presumably also on OS/X).  The issue also occurs if I do something like
>> -f rawvideo out.avi on Windows, and I'm sure that there are plenty of
>> other examples.
>>
>> Aaron Levinson
> 
> Has anyone had a chance to review this patch yet, which I submitted on March 
> 26th?  To demonstrate the impact of this patch, here's some output of before 
> and after for an .h264 file with interlaced 1080i59.94 video content:
> 
> Command-line:  ffmpeg -i test8_1080i.h264 -c:v mpeg2video test8_1080i_mp2.ts
> 
> Before patch:
> 
> --
> 
> Input #0, h264, from 'test8_1080i.h264':
>   Duration: N/A, bitrate: N/A
> Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 
> DAR 16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
> Stream mapping:
>   Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
> Press [q] to stop, [?] for help
> Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
>   Metadata:
> encoder : Lavf57.72.100
> Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR 
> 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
> Metadata:
>   encoder : Lavc57.92.100 mpeg2video
> Side data:
>   cpb: bitrate max/min/avg: 0/0/20 buffer size: 0 vbv_delay: -1
> 
> --
> 
> After patch:
> 
> --
> 
> Input #0, h264, from 'test8_1080i.h264':
>   Duration: N/A, bitrate: N/A
> Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 
> DAR 16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
> Stream mapping:
>   Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
> Press [q] to stop, [?] for help
> Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
>   Metadata:
> encoder : Lavf57.72.100
> Stream #0:0: Video: mpeg2video (Main), yuv420p(top coded first 
> (swapped)), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k 
> tbn, 29.97 tbc
> Metadata:
>   encoder : Lavc57.92.100 mpeg2video
> Side data:
>   cpb: bitrate max/min/avg: 0/0/20 buffer size: 0 vbv_delay: -1
> 
> --
> 
> As can be seen, before the patch, after decoding the .h264 file and then 
> re-encoding it as mpeg2video in an mpegts container, the interlaced aspect of 
> the video has been lost in the output, and it is now effectively 1080p29.97, 
> although the video hasn't actually been converted to progressive.  ffmpeg 
> simply thinks that the video is progressive when it is not.  With the patch, 
> the interlaced aspect is not lost and propagates to the output.  So, this 
> conclusively demonstrates that the issue has nothing to do with Blackmagic 
> and is a more general issue with interlaced video and decoding.
> 
> I can make the input file available if that would be helpful.
> 
> Anyway, it would be great if this bug fix could make it into ffmpeg.
> 
> Thanks,
> Aaron Levinson

I've provided a new version of the patch.  When I created the first version of 
the patch on March 26th, this was the first patch that I submitted to ffmpeg, 
and some aspects were rough.  I had indicated that the patch passed regression 
tests, but all I did was run "make fate", instead of "make fate 
SAMPLES=fate-suite/", and once I understood that I should use fate-suite, I 
discovered that some of the FATE tests failed with this patch.  I fixed the 
issues with the patch, adjusted some comments, and adjusted the patch 
description text.  I've confirmed that this patch passes all fate-suite tests 
for 64-bit MSVC on Windows and 64-bit gcc on Linux.

Thanks,
Aaron Levinson

Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Aaron Levinson]

On 3/26/2017 10:34 AM, Aaron Levinson wrote:
> On 3/26/2017 4:41 AM, Matthias Hunstock wrote:
>> Am 26.03.2017 um 11:50 schrieb Aaron Levinson:
>>> When using the following command to play back either file:
>>>  ffmpeg -i  -f decklink -pix_fmt uyvy422 "DeckLink SDI
>>>  4K", I noticed that with the mpegts file with the AAC audio stream,
>>>  it would correctly select an interlaced video mode for the video
>>>  output stream, but with the mpegts file with the Opus audio stream,
>>>  it would use a progressive video mode (1080p29.97) for the video
>>>  output stream.
>>
>> Which FFmpeg version did you test this with?
>>
>> There was a change related to this just short time ago.
>>
>> Does it happen with current git HEAD?
>>
>> Matthias
> 
> This issue occurs with the current git HEAD.  I'm aware of the
> Blackmagic improvement that was added in February to add support for
> interlaced video modes on output, and actually that's one of the reasons
> why I'm using the latest git sources, as opposed to, say, 3.2.4.  This
> particular issue has nothing to do with Blackmagic, and I only used
> Blackmagic in the example that reproduces the bug because it is
> something that can be reproduced on both Windows and Linux (and
> presumably also on OS/X).  The issue also occurs if I do something like
> -f rawvideo out.avi on Windows, and I'm sure that there are plenty of
> other examples.
> 
> Aaron Levinson

Has anyone had a chance to review this patch yet, which I submitted on March 
26th?  To demonstrate the impact of this patch, here's some output of before 
and after for an .h264 file with interlaced 1080i59.94 video content:

Command-line:  ffmpeg -i test8_1080i.h264 -c:v mpeg2video test8_1080i_mp2.ts

Before patch:

--

Input #0, h264, from 'test8_1080i.h264':
  Duration: N/A, bitrate: N/A
Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 
16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
Press [q] to stop, [?] for help
Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
  Metadata:
encoder : Lavf57.72.100
Stream #0:0: Video: mpeg2video (Main), yuv420p, 1920x1080 [SAR 1:1 DAR 
16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
Metadata:
  encoder : Lavc57.92.100 mpeg2video
Side data:
  cpb: bitrate max/min/avg: 0/0/20 buffer size: 0 vbv_delay: -1

--

After patch:

--

Input #0, h264, from 'test8_1080i.h264':
  Duration: N/A, bitrate: N/A
Stream #0:0: Video: h264 (High), yuv420p(top first), 1920x1080 [SAR 1:1 DAR 
16:9], 29.97 fps, 29.97 tbr, 1200k tbn, 59.94 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
Press [q] to stop, [?] for help
Output #0, mpegts, to 'test8_1080i_mp2_2.ts':
  Metadata:
encoder : Lavf57.72.100
Stream #0:0: Video: mpeg2video (Main), yuv420p(top coded first (swapped)), 
1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
Metadata:
  encoder : Lavc57.92.100 mpeg2video
Side data:
  cpb: bitrate max/min/avg: 0/0/20 buffer size: 0 vbv_delay: -1

--

As can be seen, before the patch, after decoding the .h264 file and then 
re-encoding it as mpeg2video in an mpegts container, the interlaced aspect of 
the video has been lost in the output, and it is now effectively 1080p29.97, 
although the video hasn't actually been converted to progressive.  ffmpeg 
simply thinks that the video is progressive when it is not.  With the patch, 
the interlaced aspect is not lost and propagates to the output.  So, this 
conclusively demonstrates that the issue has nothing to do with Blackmagic and 
is a more general issue with interlaced video and decoding.

I can make the input file available if that would be helpful.

Anyway, it would be great if this bug fix could make it into ffmpeg.

Thanks,
Aaron Levinson
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Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Aaron Levinson]

On 3/26/2017 4:41 AM, Matthias Hunstock wrote:

Am 26.03.2017 um 11:50 schrieb Aaron Levinson:

When using the following command to play back either file:
 ffmpeg -i  -f decklink -pix_fmt uyvy422 "DeckLink SDI
 4K", I noticed that with the mpegts file with the AAC audio stream,
 it would correctly select an interlaced video mode for the video
 output stream, but with the mpegts file with the Opus audio stream,
 it would use a progressive video mode (1080p29.97) for the video
 output stream.


Which FFmpeg version did you test this with?

There was a change related to this just short time ago.

Does it happen with current git HEAD?

Matthias


This issue occurs with the current git HEAD.  I'm aware of the 
Blackmagic improvement that was added in February to add support for 
interlaced video modes on output, and actually that's one of the reasons 
why I'm using the latest git sources, as opposed to, say, 3.2.4.  This 
particular issue has nothing to do with Blackmagic, and I only used 
Blackmagic in the example that reproduces the bug because it is 
something that can be reproduced on both Windows and Linux (and 
presumably also on OS/X).  The issue also occurs if I do something like 
-f rawvideo out.avi on Windows, and I'm sure that there are plenty of 
other examples.


Aaron Levinson
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Re: [FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Matthias Hunstock]

Am 26.03.2017 um 11:50 schrieb Aaron Levinson:
> When using the following command to play back either file:
>  ffmpeg -i  -f decklink -pix_fmt uyvy422 "DeckLink SDI
>  4K", I noticed that with the mpegts file with the AAC audio stream,
>  it would correctly select an interlaced video mode for the video
>  output stream, but with the mpegts file with the Opus audio stream,
>  it would use a progressive video mode (1080p29.97) for the video
>  output stream.  

Which FFmpeg version did you test this with?

There was a change related to this just short time ago.

Does it happen with current git HEAD?

Matthias
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[FFmpeg-devel] [PATCH] Fixed bug encountered when decoding interlaced video

[Aaron Levinson]

Hopefully I went through the patch process correctly, as this is the first time 
that I've done this.  I didn't submit a ticket regarding this issue, but a 
detailed description of the problem can be found below.  It is possible that 
there is an already existing ticket that corresponds to this issue, but I 
didn't check.  I appreciate any comments.

Thanks,
Aaron Levinson
--- next part 
From 66796ca78e9b307ba0a8a7c33bd89d006c44ddf8 Mon Sep 17 00:00:00 2001
From: Aaron Levinson 
Date: Sun, 26 Mar 2017 01:57:19 -0700
Subject: [PATCH] Fixed bug encountered when decoding interlaced video.

Purpose: Fixed bug encountered when decoding interlaced video.  In
 some cases, ffmpeg was treating it as progressive.  As a result of
 the change, the issues with interlaced video are fixed.  It is also
 possible that this change fixes other issues besides interlaced
 video.

Detailed description of problem: I generated two mpegts files, each
 with H.264 encoded 1080i59.94 video.  One of the mpegts files had an
 AAC audio stream, while the other mpegts file had an Opus audio
 stream.  When using the following command to play back either file:
 ffmpeg -i  -f decklink -pix_fmt uyvy422 "DeckLink SDI
 4K", I noticed that with the mpegts file with the AAC audio stream,
 it would correctly select an interlaced video mode for the video
 output stream, but with the mpegts file with the Opus audio stream,
 it would use a progressive video mode (1080p29.97) for the video
 output stream.  The reason why it works for AAC (usually, not always)
 and doesn't work for Opus has to do with the order in which
 init_output_stream() is called for each output stream.  When AAC is
 used, it usually calls init_output_stream() for video before it calls
 it for audio.  When Opus is used, it usually calls
 init_output_stream() for audio before it calls it for video.  When
 init_output_stream() is called for audio before it is called for
 video, this results in check_init_output_file() being called
 successfully (as in, all output streams are initialized, and it
 writes the header) before it creates the filtered frame at the end of
 reap_filters().  The process of creating and processing the filtered
 frame is what sets up interlaced video properly, but in this
 particular case, that happens after writing the header in
 check_init_output_file(), and by that point, it is too late.

Testing notes: Ran regression tests, all of which passed

Comments:
ffmpeg.c:
a) Enhanced init_output_stream() to take an additional input indicating
 whether or not check_init_output_file() should be called.  There are
 other places that call init_output_stream(), and it was important to
 make sure that these continued to work properly.
b) Adjusted reap_filters() such that, in the case that
 init_output_stream() is called, it indicates that it should not call
 check_init_output_file() in init_output_stream().  Instead, it makes
 the call to check_init_output_file() directly, but after it does the
 filtered frame setup and processing.

---
 ffmpeg.c | 42 ++
 1 file changed, 34 insertions(+), 8 deletions(-)

diff --git a/ffmpeg.c b/ffmpeg.c
index 62e7d82..a5ac5e0 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c
@@ -1395,7 +1395,7 @@ static void do_video_stats(OutputStream *ost, int 
frame_size)
 }
 }
 
-static int init_output_stream(OutputStream *ost, char *error, int error_len);
+static int init_output_stream(OutputStream *ost, char *error, int error_len, 
int do_check_output_file);
 
 static void finish_output_stream(OutputStream *ost)
 {
@@ -1410,6 +1410,8 @@ static void finish_output_stream(OutputStream *ost)
 }
 }
 
+static int check_init_output_file(OutputFile *of, int file_index);
+
 /**
  * Get and encode new output from any of the filtergraphs, without causing
  * activity.
@@ -1428,6 +1430,7 @@ static int reap_filters(int flush)
 AVFilterContext *filter;
 AVCodecContext *enc = ost->enc_ctx;
 int ret = 0;
+int did_init_output_stream = 0;
 
 if (!ost->filter || !ost->filter->graph->graph)
 continue;
@@ -1435,12 +1438,14 @@ static int reap_filters(int flush)
 
 if (!ost->initialized) {
 char error[1024] = "";
-ret = init_output_stream(ost, error, sizeof(error));
+ret = init_output_stream(ost, error, sizeof(error), 0);
 if (ret < 0) {
 av_log(NULL, AV_LOG_ERROR, "Error initializing output stream 
%d:%d -- %s\n",
ost->file_index, ost->index, error);
 exit_program(1);
 }
+
+did_init_output_stream = 1;
 }
 
 if (!ost->filtered_frame && !(ost->filtered_frame = av_frame_alloc())) 
{
@@ -1517,6 +1522,25 @@ static int reap_filters(int flush)
 
 av_frame_unref(filtered_frame);
 }
+
+// It is important to call check_init_output_file()