[FFmpeg-devel] [DEVEL][PATCH v2] ffmpeg: fix channel_layout bug on non-default layout

[pkv.stream]

Le 10/11/2017 à 1:12 AM, Michael Niedermayer a écrit :
> On Thu, Nov 09, 2017 at 09:37:33PM +0100, pkv.stream wrote:
>> Hi Michael,
>>
>>>>   ffmpeg_opt.c |   11 ++++++++++-
>>>>   1 file changed, 10 insertions(+), 1 deletion(-)
>>>> 2af07f4366efdfaf1018bb2ea29be672befe0823  0001-ffmpeg-fix-channel_layout-bug-on-non-default-layout.patch
>>>>  From 4ec55dc88923108132307b41300a1abddf32e6f7 Mon Sep 17 00:00:00 2001
>>>> From: pkviet <pkv.stream at gmail.com>
>>>> Date: Mon, 2 Oct 2017 11:14:31 +0200
>>>> Subject: [PATCH] ffmpeg: fix channel_layout bug on non-default layout
>>>>
>>>> Fix for ticket 6706.
>>>> The -channel_layout option was not working when the channel layout was not
>>>> a default one (ex: for 4 channels, quad was interpreted as 4.0 which is
>>>> the default layout for 4 channels; or octagonal interpreted as 7.1).
>>>> This led to the spurious auto-insertion of an auto-resampler filter
>>>> remapping the channels even if input and output had identical channel
>>>> layouts.
>>>> The fix operates by directly calling the channel layout if defined in
>>>> options. If the layout is undefined, the default layout is selected as
>>>> before the fix.
>>>> ---
>>>>   ffmpeg_opt.c | 11 ++++++++++-
>>>>   1 file changed, 10 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/ffmpeg_opt.c b/ffmpeg_opt.c
>>>> index 100fa76..cf5a63c 100644
>>>> --- a/ffmpeg_opt.c
>>>> +++ b/ffmpeg_opt.c
>>>> @@ -1804,6 +1804,12 @@ static OutputStream *new_audio_stream(OptionsContext *o, AVFormatContext *oc, in
>>>>           MATCH_PER_STREAM_OPT(audio_channels, i, audio_enc->channels, oc, st);
>>>> +        AVDictionaryEntry *output_layout = av_dict_get(o->g->codec_opts,
>>>> +                                                       "channel_layout",
>>>> +                                                       NULL, AV_DICT_MATCH_CASE);
>>> This doesnt look right
>>>
>>> not an issue of the patch as such but
>>> why is the channel_layout option per file and not per stream?
>>
>> just my ignorance; do you mean this is not the right way to retrieve
>> the channel_layout option from an audio stream ?
> I think there is more buggy with how the channel_layout is handled
>
> try this:
> ./ffmpeg -i ~/videos/matrixbench_mpeg2.mpg -channel_layout 5 test.wav
> and this:
> ./ffmpeg -i ~/videos/matrixbench_mpeg2.mpg -channel_layout:a 5 test.wav
>
> while it may appear that the are both working this is deceiving.
> I think only the channel number gets actually used in the 2nd case
>
> Look at what your code with av_dict_get() reads.
> It does not obtain the 5 in the 2nd case

ok I fixed that by using the flag AV_DICT_IGNORE_SUFFIX ; now 
-channel_layout:a works as expected.
I fixed also all the styling issues you spotted (mixed declarations, {} 
for if etc).

Still not understanding your initial comment though :
'why is the channel_layout option per file and not per stream?'

do you mean o->g->codec_opts is not where I should retrieve the 
channel_layout ? if not where from ?

Thanks

> [...]
>
>
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-------------- next part --------------
From 6d4f1c14135f9473b77e1c649d0e7bbaeba00a50 Mon Sep 17 00:00:00 2001
From: pkviet <pkv.stream at gmail.com>
Date: Mon, 2 Oct 2017 11:14:31 +0200
Subject: [PATCH] ffmpeg: fix channel_layout bug on non-default layout

Fix for ticket 6706.
The -channel_layout option was not working when the channel layout was not
a default one (ex: for 4 channels, quad was interpreted as 4.0 which is
the default layout for 4 channels; or octagonal interpreted as 7.1).
This led to the spurious auto-insertion of an auto-resampler filter
remapping the channels even if input and output had identical channel
layouts.
The fix operates by directly calling the channel layout if defined in
options. If the layout is undefined, the default layout is selected as
before the fix.
---
 fftools/ffmpeg_opt.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
index ca6f10d..cb25d7b 100644
--- a/fftools/ffmpeg_opt.c
+++ b/fftools/ffmpeg_opt.c
@@ -1785,6 +1785,7 @@ static OutputStream *new_audio_stream(OptionsContext *o, AVFormatContext *oc, in
     AVStream *st;
     OutputStream *ost;
     AVCodecContext *audio_enc;
+    AVDictionaryEntry *output_layout;
 
     ost = new_output_stream(o, oc, AVMEDIA_TYPE_AUDIO, source_index);
     st  = ost->st;
@@ -1799,7 +1800,10 @@ static OutputStream *new_audio_stream(OptionsContext *o, AVFormatContext *oc, in
         char *sample_fmt = NULL;
 
         MATCH_PER_STREAM_OPT(audio_channels, i, audio_enc->channels, oc, st);
-
+        output_layout = av_dict_get(o->g->codec_opts,"channel_layout", NULL, AV_DICT_IGNORE_SUFFIX);
+        if (output_layout) {
+            audio_enc->channel_layout = strtoull(output_layout->value, NULL, 10);
+        }
         MATCH_PER_STREAM_OPT(sample_fmts, str, sample_fmt, oc, st);
         if (sample_fmt &&
             (audio_enc->sample_fmt = av_get_sample_fmt(sample_fmt)) == AV_SAMPLE_FMT_NONE) {
@@ -2523,7 +2527,11 @@ loop_end:
                            (count + 1) * sizeof(*f->sample_rates));
                 }
                 if (ost->enc_ctx->channels) {
-                    f->channel_layout = av_get_default_channel_layout(ost->enc_ctx->channels);
+                    if (ost->enc_ctx->channel_layout) {
+                        f->channel_layout = ost->enc_ctx->channel_layout;
+                    } else {
+                        f->channel_layout = av_get_default_channel_layout(ost->enc_ctx->channels);
+                    }
                 } else if (ost->enc->channel_layouts) {
                     count = 0;
                     while (ost->enc->channel_layouts[count])
-- 
2.10.1.windows.1