[Libav-user] FFMPEG decode video packet with avcodec_send_packet avcodec_receive_frame

[Richard Hussong]

The correct process is described at
https://ffmpeg.org/doxygen/3.3/group__lavc__encdec.html.

To summarize: after each call to avcodec_send_packet, you loop, calling
avcodec_receive_frame and processing returned frames until you get
AVERROR(AGAIN) or an error. When you get AVERROR(AGAIN), it is time to call
avcodec_send_packet with the next received packet, then start the loop
again. Any other non-zero return from avcodec_receive_frame is a real
error, which you have to deal with as you wish. Note that you can receive
0, 1, or more frames for each packet you send, depending on the codec.

When encoding, it is the same, with avcodec_send_frame and
avcodec_receive_packet.

- Richard

On Tue, Sep 8, 2020 at 6:09 AM Jérôme SALAYET <jerome.salayet at hymatom.fr>
wrote:

> Hello,
>
> I recently want to use the last FFMPEG release version to decode video
> packets. avcodec_decode_video2 is deprecated so I want to use avcodec_send_packet
> and avcodec_receive_frame
>
>
>
> I’m just not sure waht about doing when receiving eror like
> AVERROR(EAGAIN), AVERROR_EOF… my code is below.
>
>
>
> int FFMpegImgDecode( AVCodecContext* lpCodecCtx, AVPacket* lpAVPacket,
> AVFrame* lpAVFrame)
>
> { int iResult       = 1;
>
>   int iDecodeResult = 1;
>
>
>
>
>
>   if ((lpCodecCtx!=NULL) && (lpAVFrame!=NULL) && (lpAVPacket!=NULL))
>
>    { if (m_lpCodecCtx->codec_type == AVMEDIA_TYPE_VIDEO)
>
>       { iResult = lpfnavcodec_send_packet( m_lpCodecCtx, &m_lpPacket);
>
>         if (iResult == AVERROR_EOF)
>
>          { iResult = 0;
>
>          }
>
>        if (iResult == 0) // success
>
>          { iDecodeResult = lpfnavcodec_receive_frame(m_lpCodecCtx,
> m_lpFrame);
>
>            // iDecodeResult == 0                => Success
>
>           // iDecodeResult == AVERROR(EAGAIN)) => Need to feed the next
> input frame
>
>           // else                              => Error
>
>            if (iDecodeResult==AVERROR(EAGAIN))
>
>             { printf("avcodec_receive_frame ERROR [AVERROR(EAGAIN)]\r\n");
>
>             }
>
>            if ((iDecodeResult!=0) && (iDecodeResult!=AVERROR(EAGAIN)))
>
>             { char szErrorText[255];
>
>               av_strerror( iResult, szErrorText, sizeof(szErrorText));
>
>               printf("avcodec_receive_frame ERROR [%i][%s]\r\n", iResult,
> szErrorText);
>
>             }
>
>          }
>
>        else
>
>          { char szErrorText[255];
>
>            av_strerror( iResult, szErrorText, sizeof(szErrorText));
>
>            printf("avcodec_send_packet ERROR [%i][%s]\r\n", iResult,
> szErrorText);
>
>            iDecodeResult = iResult;
>
>
>
>         }
>
>       }
>
>    }
>
>   return iDecodeResult;
>
> }
>
>
>
> Also sometimes I receive error : avcodec_send_packet ERROR
> [-1094995529][Invalid data found when processing input].
>
> It is when I decompress a h264 video stream from a camera. Do you think it
> is possible that this error can arrive if I have some network trouble with
> the camera.
>
>
>
> Regards,
>
>
>
>
>
>
>
>
>
>
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>
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