Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Tobias Rapp]

On 10.02.2016 11:40, Paul B Mahol wrote:

On 2/10/16, Tobias Rapp  wrote:

On 10.02.2016 10:59, Paul B Mahol wrote:

On 2/10/16, Tobias Rapp  wrote:

On 10.02.2016 10:01, Paul B Mahol wrote:

On 2/10/16, Tobias Rapp  wrote:

On 06.02.2016 23:30, Paul B Mahol wrote:

On 2/6/16, Paul B Mahol  wrote:

Hi,

patch attached.



Improved version attached.

[...]
+
+static int string(const char *value1, const char *value2, size_t
length)
+{
+return !strncmp(value1, value2, length);
+}


If I understand correctly this function is used to compare if the start
of value2 matches value1. Maybe this function should be called
"starts_with" (also in the "function" option enum)?


+
+static int equal(const char *value1, const char *value2, size_t
length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 != f2;
+}
+
+static int less(const char *value1, const char *value2, size_t
length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 > f2;
+}
+
+static int greater(const char *value1, const char *value2, size_t
length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 < f2;
+}
+
[...]


I think it would be better to not compare float values directly with
"==", "<" or ">". Instead use some code like "fabsf(f1 - f2) <=
epsilon".

BTW: Is the return value of "equal", "less" and "greater" inverse on
purpose?


Not for equal, but for other it is.


OK, now I got it that the argument order is flipped but matches the
documentation. In that case it is a bit counter-intuitive that one has
to do something like

mode=print:key=mykey:value=1.0:function=less

to print all metadata values of "mykey" which are *bigger* than 1.0.



Nope, this works fine here. It prints values less than 1.0


Then I have problems understanding the documentation text of "less" and
"greater".


Ah, the problem was in documenation and code, hopefully it should be clear now.


Yes, with commit 408ea50ca6bcc666babc8b8e654eb135164480af everything is 
fine.


Thanks for writing the metadata filter! Last week I had an idea for a 
similar filter but had not started implementation yet -- thus my 
interest in it.


Regards,
Tobias

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Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Tobias Rapp]

On 10.02.2016 10:01, Paul B Mahol wrote:

On 2/10/16, Tobias Rapp  wrote:

On 06.02.2016 23:30, Paul B Mahol wrote:

On 2/6/16, Paul B Mahol  wrote:

Hi,

patch attached.



Improved version attached.

[...]
+
+static int string(const char *value1, const char *value2, size_t length)
+{
+return !strncmp(value1, value2, length);
+}


If I understand correctly this function is used to compare if the start
of value2 matches value1. Maybe this function should be called
"starts_with" (also in the "function" option enum)?


+
+static int equal(const char *value1, const char *value2, size_t length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 != f2;
+}
+
+static int less(const char *value1, const char *value2, size_t length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 > f2;
+}
+
+static int greater(const char *value1, const char *value2, size_t length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 < f2;
+}
+
[...]


I think it would be better to not compare float values directly with
"==", "<" or ">". Instead use some code like "fabsf(f1 - f2) <= epsilon".

BTW: Is the return value of "equal", "less" and "greater" inverse on
purpose?


Not for equal, but for other it is.


OK, now I got it that the argument order is flipped but matches the 
documentation. In that case it is a bit counter-intuitive that one has 
to do something like


mode=print:key=mykey:value=1.0:function=less

to print all metadata values of "mykey" which are *bigger* than 1.0.



Another sidenote: I have seen that some filters use a common expression
language (e.g. aeval, crop, scale). Not sure if this expression language
supports string operators or if it is limited to numbers but in my
opinion it would be great to re-use it here.


Added and applied. Filter is easily extendable.


Thanks for adding expression support.

I know my response has come late and I'm only an occasional FFmpeg 
developer so my thoughts might not have big weight. Still I think it 
would have been more polite to first respond on the list to all my 
comments (see the "starts_with" suggestion above) before applying the patch.


Regards,
Tobias

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Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Paul B Mahol]

On 2/10/16, Tobias Rapp  wrote:
> On 10.02.2016 10:01, Paul B Mahol wrote:
>> On 2/10/16, Tobias Rapp  wrote:
>>> On 06.02.2016 23:30, Paul B Mahol wrote:
 On 2/6/16, Paul B Mahol  wrote:
> Hi,
>
> patch attached.
>

 Improved version attached.

 [...]
 +
 +static int string(const char *value1, const char *value2, size_t
 length)
 +{
 +return !strncmp(value1, value2, length);
 +}
>>>
>>> If I understand correctly this function is used to compare if the start
>>> of value2 matches value1. Maybe this function should be called
>>> "starts_with" (also in the "function" option enum)?
>>>
 +
 +static int equal(const char *value1, const char *value2, size_t length)
 +{
 +float f1, f2;
 +
 +if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
 +return 0;
 +
 +return f1 != f2;
 +}
 +
 +static int less(const char *value1, const char *value2, size_t length)
 +{
 +float f1, f2;
 +
 +if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
 +return 0;
 +
 +return f1 > f2;
 +}
 +
 +static int greater(const char *value1, const char *value2, size_t
 length)
 +{
 +float f1, f2;
 +
 +if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
 +return 0;
 +
 +return f1 < f2;
 +}
 +
 [...]
>>>
>>> I think it would be better to not compare float values directly with
>>> "==", "<" or ">". Instead use some code like "fabsf(f1 - f2) <= epsilon".
>>>
>>> BTW: Is the return value of "equal", "less" and "greater" inverse on
>>> purpose?
>>
>> Not for equal, but for other it is.
>
> OK, now I got it that the argument order is flipped but matches the
> documentation. In that case it is a bit counter-intuitive that one has
> to do something like
>
> mode=print:key=mykey:value=1.0:function=less
>
> to print all metadata values of "mykey" which are *bigger* than 1.0.
>

Nope, this works fine here. It prints values less than 1.0

>>>
>>> Another sidenote: I have seen that some filters use a common expression
>>> language (e.g. aeval, crop, scale). Not sure if this expression language
>>> supports string operators or if it is limited to numbers but in my
>>> opinion it would be great to re-use it here.
>>
>> Added and applied. Filter is easily extendable.
>
> Thanks for adding expression support.
>
> I know my response has come late and I'm only an occasional FFmpeg
> developer so my thoughts might not have big weight. Still I think it
> would have been more polite to first respond on the list to all my
> comments (see the "starts_with" suggestion above) before applying the patch.

You can post another patch anytime here and if it makes sense I will
gladly apply it.
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Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Tobias Rapp]

On 06.02.2016 23:30, Paul B Mahol wrote:

On 2/6/16, Paul B Mahol  wrote:

Hi,

patch attached.



Improved version attached.

[...]
+
+static int string(const char *value1, const char *value2, size_t length)
+{
+return !strncmp(value1, value2, length);
+}


If I understand correctly this function is used to compare if the start 
of value2 matches value1. Maybe this function should be called 
"starts_with" (also in the "function" option enum)?



+
+static int equal(const char *value1, const char *value2, size_t length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 != f2;
+}
+
+static int less(const char *value1, const char *value2, size_t length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 > f2;
+}
+
+static int greater(const char *value1, const char *value2, size_t length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 < f2;
+}
+
[...]


I think it would be better to not compare float values directly with 
"==", "<" or ">". Instead use some code like "fabsf(f1 - f2) <= epsilon".


BTW: Is the return value of "equal", "less" and "greater" inverse on 
purpose?


Another sidenote: I have seen that some filters use a common expression 
language (e.g. aeval, crop, scale). Not sure if this expression language 
supports string operators or if it is limited to numbers but in my 
opinion it would be great to re-use it here.


Regards,
Tobias

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Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Paul B Mahol]

On 2/10/16, Tobias Rapp  wrote:
> On 10.02.2016 10:59, Paul B Mahol wrote:
>> On 2/10/16, Tobias Rapp  wrote:
>>> On 10.02.2016 10:01, Paul B Mahol wrote:
 On 2/10/16, Tobias Rapp  wrote:
> On 06.02.2016 23:30, Paul B Mahol wrote:
>> On 2/6/16, Paul B Mahol  wrote:
>>> Hi,
>>>
>>> patch attached.
>>>
>>
>> Improved version attached.
>>
>> [...]
>> +
>> +static int string(const char *value1, const char *value2, size_t
>> length)
>> +{
>> +return !strncmp(value1, value2, length);
>> +}
>
> If I understand correctly this function is used to compare if the start
> of value2 matches value1. Maybe this function should be called
> "starts_with" (also in the "function" option enum)?
>
>> +
>> +static int equal(const char *value1, const char *value2, size_t
>> length)
>> +{
>> +float f1, f2;
>> +
>> +if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
>> +return 0;
>> +
>> +return f1 != f2;
>> +}
>> +
>> +static int less(const char *value1, const char *value2, size_t
>> length)
>> +{
>> +float f1, f2;
>> +
>> +if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
>> +return 0;
>> +
>> +return f1 > f2;
>> +}
>> +
>> +static int greater(const char *value1, const char *value2, size_t
>> length)
>> +{
>> +float f1, f2;
>> +
>> +if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
>> +return 0;
>> +
>> +return f1 < f2;
>> +}
>> +
>> [...]
>
> I think it would be better to not compare float values directly with
> "==", "<" or ">". Instead use some code like "fabsf(f1 - f2) <=
> epsilon".
>
> BTW: Is the return value of "equal", "less" and "greater" inverse on
> purpose?

 Not for equal, but for other it is.
>>>
>>> OK, now I got it that the argument order is flipped but matches the
>>> documentation. In that case it is a bit counter-intuitive that one has
>>> to do something like
>>>
>>> mode=print:key=mykey:value=1.0:function=less
>>>
>>> to print all metadata values of "mykey" which are *bigger* than 1.0.
>>>
>>
>> Nope, this works fine here. It prints values less than 1.0
>
> Then I have problems understanding the documentation text of "less" and
> "greater".

Ah, the problem was in documenation and code, hopefully it should be clear now.
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Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Tobias Rapp]

On 10.02.2016 10:59, Paul B Mahol wrote:

On 2/10/16, Tobias Rapp  wrote:

On 10.02.2016 10:01, Paul B Mahol wrote:

On 2/10/16, Tobias Rapp  wrote:

On 06.02.2016 23:30, Paul B Mahol wrote:

On 2/6/16, Paul B Mahol  wrote:

Hi,

patch attached.



Improved version attached.

[...]
+
+static int string(const char *value1, const char *value2, size_t
length)
+{
+return !strncmp(value1, value2, length);
+}


If I understand correctly this function is used to compare if the start
of value2 matches value1. Maybe this function should be called
"starts_with" (also in the "function" option enum)?


+
+static int equal(const char *value1, const char *value2, size_t length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 != f2;
+}
+
+static int less(const char *value1, const char *value2, size_t length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 > f2;
+}
+
+static int greater(const char *value1, const char *value2, size_t
length)
+{
+float f1, f2;
+
+if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
+return 0;
+
+return f1 < f2;
+}
+
[...]


I think it would be better to not compare float values directly with
"==", "<" or ">". Instead use some code like "fabsf(f1 - f2) <= epsilon".

BTW: Is the return value of "equal", "less" and "greater" inverse on
purpose?


Not for equal, but for other it is.


OK, now I got it that the argument order is flipped but matches the
documentation. In that case it is a bit counter-intuitive that one has
to do something like

mode=print:key=mykey:value=1.0:function=less

to print all metadata values of "mykey" which are *bigger* than 1.0.



Nope, this works fine here. It prints values less than 1.0


Then I have problems understanding the documentation text of "less" and 
"greater".




Another sidenote: I have seen that some filters use a common expression
language (e.g. aeval, crop, scale). Not sure if this expression language
supports string operators or if it is limited to numbers but in my
opinion it would be great to re-use it here.


Added and applied. Filter is easily extendable.


Thanks for adding expression support.

I know my response has come late and I'm only an occasional FFmpeg
developer so my thoughts might not have big weight. Still I think it
would have been more polite to first respond on the list to all my
comments (see the "starts_with" suggestion above) before applying the patch.


You can post another patch anytime here and if it makes sense I will
gladly apply it.


OK.

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Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Paul B Mahol]

On 2/10/16, Tobias Rapp  wrote:
> On 06.02.2016 23:30, Paul B Mahol wrote:
>> On 2/6/16, Paul B Mahol  wrote:
>>> Hi,
>>>
>>> patch attached.
>>>
>>
>> Improved version attached.
>>
>> [...]
>> +
>> +static int string(const char *value1, const char *value2, size_t length)
>> +{
>> +return !strncmp(value1, value2, length);
>> +}
>
> If I understand correctly this function is used to compare if the start
> of value2 matches value1. Maybe this function should be called
> "starts_with" (also in the "function" option enum)?
>
>> +
>> +static int equal(const char *value1, const char *value2, size_t length)
>> +{
>> +float f1, f2;
>> +
>> +if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
>> +return 0;
>> +
>> +return f1 != f2;
>> +}
>> +
>> +static int less(const char *value1, const char *value2, size_t length)
>> +{
>> +float f1, f2;
>> +
>> +if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
>> +return 0;
>> +
>> +return f1 > f2;
>> +}
>> +
>> +static int greater(const char *value1, const char *value2, size_t length)
>> +{
>> +float f1, f2;
>> +
>> +if (sscanf(value1, "%f", ) + sscanf(value2, "%f", ) != 2)
>> +return 0;
>> +
>> +return f1 < f2;
>> +}
>> +
>> [...]
>
> I think it would be better to not compare float values directly with
> "==", "<" or ">". Instead use some code like "fabsf(f1 - f2) <= epsilon".
>
> BTW: Is the return value of "equal", "less" and "greater" inverse on
> purpose?

Not for equal, but for other it is.

>
> Another sidenote: I have seen that some filters use a common expression
> language (e.g. aeval, crop, scale). Not sure if this expression language
> supports string operators or if it is limited to numbers but in my
> opinion it would be great to re-use it here.

Added and applied. Filter is easily extendable.
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Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Paul B Mahol]

On 2/6/16, Paul B Mahol  wrote:
> On 2/6/16, Paul B Mahol  wrote:
>> Hi,
>>
>> patch attached.
>>
>
> Improved version attached.
>

Gonna push this soon.
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Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Paul B Mahol]

On 2/6/16, Moritz Barsnick  wrote:
> On Sat, Feb 06, 2016 at 12:47:25 +0100, Paul B Mahol wrote:
>> patch attached.
>
> Nice. (Untested.)
>
>
>
>> +Manipulate frames metadata.
>   Either:
> frame metadata [using this as a generic term]
>   or:
> frames' metadata
>
> I prefer the former.
>
>> +If both @code{value} and @code{key} is set, select frame
>   ^ frames (plural)
>> +every frame that have such key in metadata.
>  has (singular)
>
>> +Print key and value if metadata was found.
> I'm not sure I've understood whether this can apply to only matching
> metadata (key, key/value), or to any metadata.
>
>> +Set metadata value which will be used. This option is mandatory for
>> modify
>> +and add mode.
>   for 'modify' and 'add' modes (note the quoting and the plural).
>
>> +Set length of how much characters of two metadata values need to match to
>> be
>   many

All should be resolved in newer version. Thanks for feedback.
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Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Paul B Mahol]

On 2/6/16, Paul B Mahol  wrote:
> Hi,
>
> patch attached.
>

Improved version attached.
From 46283dd6b38ce8f1346249707986212546026e39 Mon Sep 17 00:00:00 2001
From: Paul B Mahol 
Date: Sat, 6 Feb 2016 11:19:45 +0100
Subject: [PATCH] avfilter: add metadata filters

Signed-off-by: Paul B Mahol 
---
 doc/filters.texi |  65 +++
 libavfilter/Makefile |   2 +
 libavfilter/allfilters.c |   2 +
 libavfilter/f_metadata.c | 282 +++
 4 files changed, 351 insertions(+)
 create mode 100644 libavfilter/f_metadata.c

diff --git a/doc/filters.texi b/doc/filters.texi
index 664ebe8..fa33491 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -8444,6 +8444,71 @@ format=rgb24,mergeplanes=0x000102:yuv444p
 @end example
 @end itemize
 
+@section metadata, ametadata
+
+Manipulate frame metadata.
+
+This filter accepts the following options:
+
+@table @option
+@item m
+Set mode of operation of the filter.
+
+Can be one of the following:
+
+@table @samp
+@item select
+If both @code{value} and @code{key} is set, select frames
+which have such metadata. If only @code{key} is set, select
+every frame that has such key in metadata.
+
+@item add
+Add new metadata @code{key} and @code{value}. If key is already available
+do nothing.
+
+@item modify
+Modify value of already present key.
+
+@item delete
+If @code{value} is set, delete only keys that have such value.
+Otherwise, delete key.
+
+@item print
+Print key and value if metadata was found.
+@end table
+
+@item key
+Set key used with all modes, Must be set.
+
+@item value
+Set metadata value which will be used. This option is mandatory for
+@code{modify} and @code{add} mode.
+
+@item length
+Set length of how many characters of two metadata values need to match to be
+considered same. Default is all available characters.
+
+@item function
+Which function to use when comparing metadata value and @code{value}.
+
+Can be one of following:
+
+@table @samp
+@item string
+Values are interpreted as strings, returns true if @code{value} is same as metadata value up
+to N chars as set in @code{length} option.
+
+@item less
+Values are interpreted as floats, returns true if @code{value} is less than metadata value.
+
+@item equal
+Values are interpreted as floats, returns true if @code{value} is equal with metadata value.
+
+@item greater
+Values are interpreted as floats, returns true if @code{value} is greater than metadata value.
+@end table
+@end table
+
 @section mpdecimate
 
 Drop frames that do not differ greatly from the previous frame in
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index e76d18e..852b60d 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -39,6 +39,7 @@ OBJS-$(CONFIG_AINTERLEAVE_FILTER)+= f_interleave.o
 OBJS-$(CONFIG_ALIMITER_FILTER)   += af_alimiter.o
 OBJS-$(CONFIG_ALLPASS_FILTER)+= af_biquads.o
 OBJS-$(CONFIG_AMERGE_FILTER) += af_amerge.o
+OBJS-$(CONFIG_AMETADATA_FILTER)  += f_metadata.o
 OBJS-$(CONFIG_AMIX_FILTER)   += af_amix.o
 OBJS-$(CONFIG_ANULL_FILTER)  += af_anull.o
 OBJS-$(CONFIG_APAD_FILTER)   += af_apad.o
@@ -185,6 +186,7 @@ OBJS-$(CONFIG_LUTYUV_FILTER) += vf_lut.o
 OBJS-$(CONFIG_MASKEDMERGE_FILTER)+= vf_maskedmerge.o framesync.o
 OBJS-$(CONFIG_MCDEINT_FILTER)+= vf_mcdeint.o
 OBJS-$(CONFIG_MERGEPLANES_FILTER)+= vf_mergeplanes.o framesync.o
+OBJS-$(CONFIG_METADATA_FILTER)   += f_metadata.o
 OBJS-$(CONFIG_MPDECIMATE_FILTER) += vf_mpdecimate.o
 OBJS-$(CONFIG_NEGATE_FILTER) += vf_lut.o
 OBJS-$(CONFIG_NNEDI_FILTER)  += vf_nnedi.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 27d54bc..a904402 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -59,6 +59,7 @@ void avfilter_register_all(void)
 REGISTER_FILTER(ALIMITER,   alimiter,   af);
 REGISTER_FILTER(ALLPASS,allpass,af);
 REGISTER_FILTER(AMERGE, amerge, af);
+REGISTER_FILTER(AMETADATA,  ametadata,  af);
 REGISTER_FILTER(AMIX,   amix,   af);
 REGISTER_FILTER(ANEQUALIZER,anequalizer,af);
 REGISTER_FILTER(ANULL,  anull,  af);
@@ -206,6 +207,7 @@ void avfilter_register_all(void)
 REGISTER_FILTER(MASKEDMERGE,maskedmerge,vf);
 REGISTER_FILTER(MCDEINT,mcdeint,vf);
 REGISTER_FILTER(MERGEPLANES,mergeplanes,vf);
+REGISTER_FILTER(METADATA,   metadata,   vf);
 REGISTER_FILTER(MPDECIMATE, mpdecimate, vf);
 REGISTER_FILTER(NEGATE, negate, vf);
 REGISTER_FILTER(NNEDI,  nnedi,  vf);
diff --git a/libavfilter/f_metadata.c b/libavfilter/f_metadata.c
new file mode 100644
index 000..f7195f1

Re: [FFmpeg-devel] [PATCH] avfilter: add metadata filters

[Moritz Barsnick]

On Sat, Feb 06, 2016 at 12:47:25 +0100, Paul B Mahol wrote:
> patch attached.

Nice. (Untested.)



> +Manipulate frames metadata.
  Either:
frame metadata [using this as a generic term]
  or:
frames' metadata

I prefer the former.

> +If both @code{value} and @code{key} is set, select frame
  ^ frames (plural)
> +every frame that have such key in metadata.
 has (singular)

> +Print key and value if metadata was found.
I'm not sure I've understood whether this can apply to only matching
metadata (key, key/value), or to any metadata.

> +Set metadata value which will be used. This option is mandatory for modify
> +and add mode.
  for 'modify' and 'add' modes (note the quoting and the plural).

> +Set length of how much characters of two metadata values need to match to be
  many

Moritz
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