Custom codec. Supported by ffmpeg, incompatible with VLC

[stefano.asioli]

Hi,

I am trying to add support for a new (custom) codec to VLC under Linux. Currently, it is only
supported by ffmpeg and ffplay. To get this result, I followed these instructions :

http://wiki.multimedia.cx/index.php?tit ... odec_howto

and I modified libavcodec and libavformat. Then, I linked VLC to these modified ffmpeg libraries.
The format is now recognised by VLC, as well as frame size, duration and frame rate. However,
when playing the video, I only see a black screen.

Apparently, libavcodec and libavformat functions like mydecoder_decode_frame and
mydemux_read_packet are correctly called.

Have you got any ideas how I should modify my libavcodec and libavformat to make them fully
compatible with the VLC interface?

Thanks,

Stefano

[Jean-Baptiste Kempf]

You should add the correct fourcc in modules/codec/avcodec/foucc.c

[stefano.asioli]

Hi. Thanks for your reply.

Actually, I already did that. The format is correctly recognised.
As a test, I tried to write a yuv sequence while running both ffplay and vlc, doing something like this
inside mycodec_decode_frame:

Code: Select all

FILE *fake = fopen("fake.yuv","ab"); fwrite(picture->data[0], sizeof(uint8_t), avccontext->width * avccontext->height * 3 / 2, fake); fclose(fake);

Basically, I append a new frame to a file called fake.yuv every time I call mycodec_decode_frame.
Both fake.yuv output files are correct and contain the decoded sequence.

Do you believe it might be a problem of visualisation? Or could it be problem of timestamps?

Thanks,
Stefano

[xtophe]

Does vlc's log have any interesting messages ?

[stefano.asioli]

Hello.

Not really, however, in the end I found the problem. I had only set dts and pts timestamps in libavformat, while
apparently you also need to set pts in libavcodec. Other codecs that I checked did not require it, as they could
estimate it from the video bit-rate. Hope this will be useful to somebody else in the future.

Thanks,

Stefano