Hello,
In a processing workflow that includes first encoding a video / audio frame
followed by writing that frame to a file/network stream, it is required to set
the packet pts prior to encoding. The subsequent encoding operation then
returns an output value (gotPacket) indicating whether a packet was returned,
e.g.:
returnVal = avcodec_encode_audio2(codecCtx, &_avPacket,
_streamAudioFrame, &gotPacket);
A packet might not have been returned, but if one has been returned, there are
two notable characteristics about it:
1. it is not necessarily the same packet that was encoded; i.e. the encoder can
return a different packet (presumably due to reordering as necessary, etc.).
2. The returned packet does not have an accurate pts set, and so this must be
manually set in the code.
When dealing with a video stream, the general approach to setting packet pts is
to grab the AVCodecContext's pts of its coded frame, and then rescale it from a
value relative to the context's time_base (that's the one based on frame rate)
to one relative to the stream's time_base (the one based on time), as such:
_avPacket.pts = av_rescale_q(codecCtx->coded_frame->pts, codecCtx->time_base,
_videoStream->time_base);
The key point there is that the pts of the frame involved with the packet
returned is accessible in the context's coded_frame, i.e.:
videoCodecCtx->coded_frame->pts
That's great for video. But when processing audio, coded_frame->pts is
consistently junk, always valued -9223372036854775808. So my question is after
encoding, if the avcodec_encode_audio2 indeed returns a packet how to access
the pts for the encoded frame (or in the case of audio, it would probably be
more proper to say the encoded samples)? Again, given that the packet returned
by the encoder isn't necessarily the one that was encoded, we need the pts of
the packet when it was encoded.
How do I access this value?
Thanks,
Brad
_______________________________________________
Libav-user mailing list
[email protected]
http://ffmpeg.org/mailman/listinfo/libav-user
