[FFmpeg-devel] [PATCHv2] avcodec/utils: do not reallocate packet buffer for AV_CODEC_ID_WRAPPED_AVFRAME

Hendrik Leppkes h.leppkes at gmail.com
Sun Feb 19 15:49:34 EET 2017


On Sun, Feb 19, 2017 at 2:41 PM, wm4 <nfxjfg at googlemail.com> wrote:
> On Sun, 19 Feb 2017 14:35:42 +0100
> Marton Balint <cus at passwd.hu> wrote:
>
>> Reallocating a wrapped avframe invalidates internal pointers, such as extended
>> data.
>>
>> FFmpeg has another way of passing AVFrames to muxers, but it seems the API
>> (av_write_uncoded_frame) is not implemented in the ffmpeg CLI yet.
>>
>> Signed-off-by: Marton Balint <cus at passwd.hu>
>> ---
>>  libavcodec/utils.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavcodec/utils.c b/libavcodec/utils.c
>> index f4085bf..184821a 100644
>> --- a/libavcodec/utils.c
>> +++ b/libavcodec/utils.c
>> @@ -1820,7 +1820,7 @@ int attribute_align_arg avcodec_encode_audio2(AVCodecContext *avctx,
>>      AVFrame *padded_frame = NULL;
>>      int ret;
>>      AVPacket user_pkt = *avpkt;
>> -    int needs_realloc = !user_pkt.data;
>> +    int needs_realloc = !user_pkt.data && avctx->codec_id != AV_CODEC_ID_WRAPPED_AVFRAME;
>>
>>      *got_packet_ptr = 0;
>>
>> @@ -1964,7 +1964,7 @@ int attribute_align_arg avcodec_encode_video2(AVCodecContext *avctx,
>>  {
>>      int ret;
>>      AVPacket user_pkt = *avpkt;
>> -    int needs_realloc = !user_pkt.data;
>> +    int needs_realloc = !user_pkt.data && avctx->codec_id != AV_CODEC_ID_WRAPPED_AVFRAME;
>>
>>      *got_packet_ptr = 0;
>>
>
> I don't understand this logic in the first place. If nothing was
> encoded (!ret), and avpkt->data is set (why is it set?), then the
> AVPacket.buf is realllocated (why?) to the packet size (why???) - how
> does it make sense?

ret = 0 indicates successfull encode, ie. not an error code. What
result code did you expect?
AFAIK the realloc is performed to shrink over-sized pre-allocated
packets down and save memory.

- Hendrik


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