[Libav-user] Getting a Frame question

[Christopher Snowhill]

On 9/4/16 5:27 PM, Charles wrote:
> On 09/04/2016 10:52 AM, M N wrote:
>> Gonzalo then how should I continue to read packets from input format
>> context and write them to output format context?
>>
>> 04.09.2016, 05:14, "Charles" <linux2 at orion15.org>:
>>> On 09/03/2016 08:34 PM, Gonzalo Garramuño wrote:
>>>>  El 03/09/2016 a las 17:55, M J escribió:
>>>>>  Hi
>
> MJ,
> I probably wasn't clear, each call is dependent on the return value of
> the previous call.
> i.e. if you did not get return 0 or EAGIN from send_packet you should
> probably not call receive_frame
>
>>>>>
>>>>>  while(av_read_frame(input_ctx, pkts) == 0)
>>>>>  {
>>>>>           //decoding
>>>>>           int ret1 = avcodec_send_packet(input_codecCtx, pkts);
>>>>>           int ret2 = avcodec_receive_frame(input_codecCtx, rawFrame);
>
> Why don't you just print the return values. SEE av_strerror
> https://ffmpeg.org/doxygen/3.1/group__lavu__error.html#ga5792b4a2d18d7d9cb0efbcfc335dce24
>
>
>>>>>
>>>>>           //encoding
>>>>>           avcodec_send_frame(output_codecCtx, rawFrame);
>>>>>           avcodec_receive_packet(output_codecCtx, pktr);
>
> These have return values also.
>
>>>>>
>>>>>           int ret = av_interleaved_write_frame(output_ctx, pktr);
>>>>>  }
>>>>>  *************************************************
>>>>  Hi, MJ.
>
> Assuming everything is setup correctly, and 1 frame -> 1 packet && 1
> packet -> 1 frame
>
> while ( av_read_frame == 0 )
>    if avcodec_send_packet == 0
>       if avcodec_receive_frame == 0
>          if avcodec_send_frame == 0
>             if avcodec_receive_packet == 0
>                av_interleaved_write_frame
>
> But, each of those IF's have multiple return values
> What are you going to do if the return is AVERROR(EAGAIN) or AVERROR_EOF
> What about the frame delay on the encoder?
>
> Thanks
> cco
Don't forget, maybe he's parsing an interleaved stream, and isn't paying
attention to which stream each packet belongs to.
>
>
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