On Tue, 31 Oct 2017, Mironov, Mikhail wrote:
[...]
I see some confusion. The user can call send_frame/receive_packet in any order, and you can implement send_frame and receive_packet any way you want, the only thing you have to guarantee is that you cannot return EAGAIN for both send_frame and receive_packet. Not even temporarily. If you returned EAGAIN in send_frame, you must return success or a normal error in receive_packet. If you returned EAGAIN in receive_packet, you must return success or a normal error in send_frame. By returning EAGAIN in receive_packet you make sure that the API user submits as many frames as needed to fill your pipeline. The simplest solution really seems to me what Mark proposed: send_frame: if (have_stored_frame) return EAGAIN; if (amd_send_frame() == INPUT_FULL) store_frame; return 0; receive_packet: if (have_stored_frame) { if (amd_send_frame() == OK) unstore_frame; block_until_have_packet return packet } else { return EAGAIN } I hope I did not mess it up, proper draining and error handling obviously needs some minor changes.The logic in receive_packet() will be slightly different but I will figure this out. My only note is that returning EAGAIN from send_frame() will not work with current ffmpeg calling code. I was assured that this will never happen but I don’t like possibility of the failure. What the calling code supposed to do getting EAGAIN from send_frame()? Resubmit? If so it would not work with the logic described. Anyway, lets try Mark's suggestion and see if alternations are needed.
ffmpeg.c is written in a way that it calls receive_packet repeatedly until it gets EAGAIN. Due to the API requirements I mentioned (send_frame and receive_packet both cannot return EAGAIN), it is OK to not handle EAGAIN for send_frame in ffmpeg.c code.
Other applications might use other logic (e.g. call send_frame repeatedly, and then call receive_packet once, or call send_frame and receive packet alternating), in these cases the user application must be able to handle EAGAIN for send_frame, and resubmit the frame next time.
But if ffmpeg.c gets an EAGAIN in send_frame, that means a bug in the encoder because the encoder is breaking the API and it needs to be fixed.
Regards, Marton _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
