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ffmpeg: Add async audio decoding loop

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This leverages libavcodec >= 57.37.100's new asynchronous API,
which both allows decoding in hardware and in a separate thread,
and in any case would free up more CPU time for Panda's app loop.

This also avoids use of the now-deprecated `avcodec_decode_audio4`
This commit is contained in:
Sam Edwards 2018-03-31 03:12:00 -06:00
parent 62f9de101a
commit e430428703
1 changed files with 57 additions and 0 deletions
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57
panda/src/ffmpeg/ffmpegAudioCursor.cxx
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@ -299,6 +299,62 @@ fetch_packet() {
*/ */
bool FfmpegAudioCursor:: bool FfmpegAudioCursor::
reload_buffer() { reload_buffer() {
#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(57, 37, 100)
// lavc >= 57.37.100 deprecates the old (avcodec_decode_audio*) API in favor
// of a newer, asynchronous API. This is great for our purposes - it gives
// the codec the opportunity to decode in the background (e.g. in another
// thread or on a dedicated hardware coprocessor).
// First, let's fill the codec's input buffer with as many packets as it'll
// take:
int ret;
while (_packet->data != nullptr) {
ret = avcodec_send_packet(_audio_ctx, _packet);
if (ret != 0) {
// Nonzero return code is an error.
break;
}
// If we got here, the codec took the packet! Fetch another one.
fetch_packet();
if (_packet->data == nullptr) {
// fetch_packet() says we're out of packets. Let the codec know.
ret = avcodec_send_packet(_audio_ctx, NULL);
}
}
// Expected ret codes are 0 (we ran out of packets) and EAGAIN (codec full)
if ((ret != 0) && (ret != AVERROR(EAGAIN))) {
// Some odd error happened. We can't proceed.
ffmpeg_cat.error()
<< "avcodec_send_packet returned " << ret << "\n";
return false;
}
// Now we retrieve our frame!
ret = avcodec_receive_frame(_audio_ctx, _frame);
if (ret == AVERROR_EOF) {
// The only way for this to happen is if we're out of packets.
nassertr(_packet->data == nullptr, false);
// Synthesize silence:
_buffer_head = 0;
_buffer_tail = _buffer_size;
memset(_buffer, 0, _buffer_size * 2);
return true;
} else if (ret != 0) {
// Some odd error happened. We can't proceed.
ffmpeg_cat.error()
<< "avcodec_receive_frame returned " << ret << "\n";
return false;
}
// We now have _frame. It will be handled below.
#else
int got_frame = 0; int got_frame = 0;
while (!got_frame) { while (!got_frame) {
// If we're out of packets, generate silence. // If we're out of packets, generate silence.
@ -339,6 +395,7 @@ reload_buffer() {
_packet_data += len; _packet_data += len;
_packet_size -= len; _packet_size -= len;
} }
#endif
int bufsize; int bufsize;
#ifdef HAVE_SWRESAMPLE #ifdef HAVE_SWRESAMPLE