[Libav-user] About output_example.c

Vincent,Wei weikun0905 at gmail.com
Mon Apr 18 10:58:31 CEST 2011

 Is the function av_rescale_q() some differnet bettewn H264 and the MPEG4???

 I had passed the same paramters, but the pkt.pts is different.
pkt.pts= av_rescale_q(c->coded_frame->pts, c->time_base, st->time_base);
 Please help me!! Thanks for all of you!!

2011/4/18 Vincent,Wei <weikun0905 at gmail.com>

> Hi,all
>      I am a new user of ffmpeg, I need to change the RTP packet to the avi
> file,used the H264 encoder, so I read the code of output_example.c. And I
> had tried to genrerate a test.avi file just like the example.
>     There are some question about the result:
>     (1) When I use the .avi as the extensions, it uesd the CODEC_ID_MPEG4
> as default , I had found that it is defined at the avienc.c line:562
>        AVOutputFormat avi_muxer = {
>        .....
>       CODEC_ID_MP2,
>       CODEC_ID_MPEG4,
>        .....
>        };
>       I had try to change it to the CODEC_ID_H264, but when I try to
> genrerat the test.avi again, I found that it can't work rightly,error as
> follow:
>       error, non monotone timestamps -368934881474191031 >=
> -368934881474191031
>      Error while writing video frame .
>      Why?
> (2) When I edit the output_example.c line:445
>        fmt = guess_format("h264", filename, NULL);
>       I also set the .avi as the extensions, but it can't generate the avi
> format file(alougth the file look like .avi extension name,but the format do
> not fit the avi format standard).
>       It generate the file which fit the .264 file format ,so it is turly
> encode as the h264, but I need the avi file.
> (3) The example is worked as the YUV420 as input data, but my data source
> had already been encoded as H264(RTP packet payload),
>      I thought that I may not need to change the data to YUV first, it's
> not efficient.
>      I means that if the data is already the encoded ,the
> avcodec_encode_video() may not be called? If it is right,av_write_frame()
> need what data as the input data ? raw h264 data ?or some others??
> How can I use the ffmpeg to help me do the work?
> That is all, so many questions for all of you, please help me, thanks
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