Re: [FFmpeg-devel] [RFC][PATCH] movenc: write clap tag

[Dave Rice]

> On Jul 6, 2017, at 9:39 PM, Derek Buitenhuis  
> wrote:
> 
> On 7/7/2017 2:20 AM, Dave Rice wrote:
>> Currently this patch writes the clap atom under this condition 
>> "track->par->codec_id == AV_CODEC_ID_RAWVIDEO & track->mode == MODE_MOV”; 
>> however, AV_CODEC_ID_RAWVIDEO isn’t quite what the spec asks for. Any advice 
>> on how to write this condition for “uncompressed Y´CbCr data formats”; for 
>> instance v210 is considered uncompress Y´CbCr in QuickTime but is not a 
>> AV_CODEC_ID_RAWVIDEO. I haven’t found a concise way to add a condition for 
>> uncompressed YUV.
> 
> First, it should be '&&', I assume.

Thanks.

> I don't think there's any concise way of checking such conditions... you'll
> probably have to do something like a list of "codes" (v410, v210, raw) and
> some sort of sanity check for track->par->format to confirm is is YCbCr.
> Maybe someone knows better than myself.

I see that although it’s mandatory for uncompressed YUV, there’s no constraint 
to not use it otherwise, so I think I’ll proceed with just a check for 
MODE_MOV. I just checked ffmbc’s movenc.c and it also only checks for MODE_MOV.
Dave Rice
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Re: [FFmpeg-devel] [RFC][PATCH] movenc: write clap tag

[Derek Buitenhuis]

On 7/7/2017 2:20 AM, Dave Rice wrote:
> Currently this patch writes the clap atom under this condition 
> "track->par->codec_id == AV_CODEC_ID_RAWVIDEO & track->mode == MODE_MOV”; 
> however, AV_CODEC_ID_RAWVIDEO isn’t quite what the spec asks for. Any advice 
> on how to write this condition for “uncompressed Y´CbCr data formats”; for 
> instance v210 is considered uncompress Y´CbCr in QuickTime but is not a 
> AV_CODEC_ID_RAWVIDEO. I haven’t found a concise way to add a condition for 
> uncompressed YUV.

First, it should be '&&', I assume.

I don't think there's any concise way of checking such conditions... you'll
probably have to do something like a list of "codes" (v410, v210, raw) and
some sort of sanity check for track->par->format to confirm is is YCbCr.
Maybe someone knows better than myself.

- Derek
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[FFmpeg-devel] [RFC][PATCH] movenc: write clap tag

[Dave Rice]

Hi all,
I’m looking for some assistance on this patch which is intended to resolve 
https://trac.ffmpeg.org/ticket/6145 .

In 
https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html
 
,
 regarding the clap atom, it states "This is a mandatory extension for all 
uncompressed Y´CbCr data formats”. This patch is intended to write the clap 
atom in those cases as a coincident with the stored image (not supported a 
cropped aperature yet), but I’m having trouble associating it with the correct 
conditional formats. 

Currently this patch writes the clap atom under this condition 
"track->par->codec_id == AV_CODEC_ID_RAWVIDEO & track->mode == MODE_MOV”; 
however, AV_CODEC_ID_RAWVIDEO isn’t quite what the spec asks for. Any advice on 
how to write this condition for “uncompressed Y´CbCr data formats”; for 
instance v210 is considered uncompress Y´CbCr in QuickTime but is not a 
AV_CODEC_ID_RAWVIDEO. I haven’t found a concise way to add a condition for 
uncompressed YUV.

Other comments welcome. Thanks.

From a5e399c6eeaa64aef52dc498cc62114428f42941 Mon Sep 17 00:00:00 2001
From: Dave Rice 
Date: Thu, 6 Jul 2017 21:12:38 -0400
Subject: [PATCH] movenc: write clap tag

---
 libavformat/movenc.c | 19 +++
 1 file changed, 19 insertions(+)

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 88f2f2c819..033e8550b2 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -1669,6 +1669,21 @@ static int mov_write_sv3d_tag(AVFormatContext *s, 
AVIOContext *pb, AVSphericalMa
 return update_size(pb, sv3d_pos);
 }
 
+static int mov_write_clap_tag(AVIOContext *pb, MOVTrack *track)
+{
+avio_wb32(pb, 64);
+ffio_wfourcc(pb, "clap");
+avio_wb32(pb, track->par->width); /* aperatureWidth numerator */
+avio_wb32(pb, 1); /* aperatureWidth denominator (= 1) */
+avio_wb32(pb, track->height); /* aperatureHeight numerator */
+avio_wb32(pb, 1); /* aperatureHeight denominator (= 1) */
+avio_wb32(pb, 0); /* horizontal offset numerator (= 0) */
+avio_wb32(pb, 1); /* horizontal offset denominator (= 1) */
+avio_wb32(pb, 0); /* vertical offset numerator (= 0) */
+avio_wb32(pb, 1); /* vertical offset denominator (= 1) */
+return 64;
+}
+
 static int mov_write_pasp_tag(AVIOContext *pb, MOVTrack *track)
 {
 AVRational sar;
@@ -1939,6 +1954,10 @@ static int mov_write_video_tag(AVIOContext *pb, 
MOVMuxContext *mov, MOVTrack *tr
 av_log(mov->fc, AV_LOG_WARNING, "Not writing 'colr' atom. Format 
is not MOV or MP4.\n");
 }
 
+if (track->par->codec_id == AV_CODEC_ID_RAWVIDEO & track->mode == 
MODE_MOV) {
+mov_write_clap_tag(pb, track);
+}
+
 if (track->mode == MODE_MP4 && mov->fc->strict_std_compliance <= 
FF_COMPLIANCE_UNOFFICIAL) {
 AVStereo3D* stereo_3d = (AVStereo3D*) 
av_stream_get_side_data(track->st, AV_PKT_DATA_STEREO3D, NULL);
 AVSphericalMapping* spherical_mapping = 
(AVSphericalMapping*)av_stream_get_side_data(track->st, AV_PKT_DATA_SPHERICAL, 
NULL);
-- 
2.13.0

Best Regards,
Dave Rice

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