[FFmpeg-devel] [PATCH] avcodec/encode: only allow undersized audio frames if they are the last

[Marton Balint]

On Sat, 10 Aug 2019, Marton Balint wrote:

>
>
> On Sun, 4 Aug 2019, Marton Balint wrote:
>
>>
>>
>> On Sat, 3 Aug 2019, Lynne wrote:
>>
>>> Aug 3, 2019, 9:40 PM by cus at passwd.hu:
>>>
>>>> Otherwise the user might get a silence padded frame in the beginning or 
> in 
>> the
>>>> middle of the encoding.
>>>>
>>>> Some other bug uncovered this:
>>>>
>>>> ./ffmpeg -loglevel verbose -y -f data -i /dev/zero \
>>>> -filter_complex "nullsrc=s=60x60:d=10[v0];sine=d=10[a]" \
>>>> -map '[v0]' -c:v:0 rawvideo \
>>>> -map '[a]'  -c:a:0 mp2 \
>>>> -f mpegts out.ts
>>>>
>>>> Signed-off-by: Marton Balint <cus at passwd.hu>
>>>> ---
>>>>  libavcodec/encode.c | 10 ++++++++--
>>>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/libavcodec/encode.c b/libavcodec/encode.c
>>>> index d12c42526b..d81b32b983 100644
>>>> --- a/libavcodec/encode.c
>>>> +++ b/libavcodec/encode.c
>>>> @@ -174,8 +174,14 @@ int attribute_align_arg 
>> avcodec_encode_audio2(AVCodecContext *avctx,
>>>>  goto end;
>>>>  }
>>>>  } else if (!(avctx->codec->capabilities & 
>> AV_CODEC_CAP_VARIABLE_FRAME_SIZE)) {
>>>> -            if (frame->nb_samples < avctx->frame_size &&
>>>> -                !avctx->internal->last_audio_frame) {
>>>> +            /* if we already got an undersized frame, that must have 
> been 
>> the last */
>>>> +            if (avctx->internal->last_audio_frame) {
>>>> +                av_log(avctx, AV_LOG_ERROR, "frame_size (%d) was not 
>> respected for a non-last frame (avcodec_encode_audio2)\n", 
>> avctx->frame_size);
>>>> +                ret = AVERROR(EINVAL);
>>>> +                goto end;
>>>> +            }
>>>> +
>>>> +            if (frame->nb_samples < avctx->frame_size) {
>>>>  ret = pad_last_frame(avctx, &padded_frame, frame);
>>>>  if (ret < 0)
>>>>  goto end;
>>>>
>>>
>>> You haven't fixed the bug, you've just made it an error. You have to fix 
>> the encoder instead.
>>> The check might be useful if its made a warning instead though.
>>
>> The command line was also failing before the patch with an invalid frame 
>> size error at the end of the stream. So ffmpeg.c / libavfilter not 
>> providing fixed frame sizes is a different bug to the one this patch 
>> supposed to fix.
>>
>> This fix disallows padding a frame with silence in the middle of the 
>> encoding if the user provides an undersized frame. libavcodec should 
>> reject such encoding attempts and not corrupt the output with silence.
>>
>
> Ping, will apply soon.

Applied.

Regards,
Marton