video: refactor PTS code, add fall back heuristic to DTS

Refactor the PTS handling code to make it cleaner, and to separate the
bits that use PTS sorting.

Add a heuristic to fall back to DTS if the PTS us non-monotonic. This
code is based on what FFmpeg/Libav use for ffplay/avplay and also
best_effort_timestamp (which is only in FFmpeg). Basically, this 1. just
uses the DTS if PTS is unset, and 2. ignores PTS entirely if PTS is non-
monotonic, but DTS is sorted.

The code is pretty much the same as in Libav [1]. I'm not sure if all of
it is really needed, or if it does more than what the paragraph above
mentions. But maybe it's fine to cargo-cult this.

This heuristic fixes playback of mpeg4 in ogm, which returns packets
with PTS==DTS, even though the PTS timestamps should follow codec
reordering. This is probably a libavformat demuxer bug, but good luck
trying to fix it.

The way vd_lavc.c returns the frame PTS and DTS to dec_video.c is a bit
inelegant, but maybe better than trying to mess the PTS back into the
decoder callback again.

[1] https://git.libav.org/?p=libav.git;a=blob;f=cmdutils.c;h=3f1c667075724c5cde69d840ed5ed7d992898334;hb=fa515c2088e1d082d45741bbd5c05e13b0500804#l1431

2 files changed, 4 insertions, 6 deletions

diff --git a/mpvcore/av_common.c b/mpvcore/av_common.c
index 3e3caa8f0d..d233071c23 100644
--- a/mpvcore/av_common.c
+++ b/mpvcore/av_common.c
@@ -91,12 +91,10 @@ void mp_set_av_packet(AVPacket *dst, struct demux_packet *mpkt)
 // Return the pts/dts from a frame returned by libavcodec. Note that this
 // assumes libavcodec was fed a packet setup with mp_set_av_packet()! If not,
 // the timestamps might contain garbage.
-// Normally, this returns the pts. If the pts is unknown, return dts instead.
-double mp_get_av_frame_pkt_pdts(AVFrame *frame)
+void mp_get_av_frame_pkt_ts(AVFrame *frame, double *out_pts, double *out_dts)
 {
-    double pts = (union pts){.i = frame->pkt_pts}.d;
-    double dts = (union pts){.i = frame->pkt_dts}.d;
-    return pts == MP_NOPTS_VALUE ? dts : pts;
+    *out_pts = (union pts){.i = frame->pkt_pts}.d;
+    *out_dts = (union pts){.i = frame->pkt_dts}.d;
 }
 
 void mp_add_lavc_decoders(struct mp_decoder_list *list, enum AVMediaType type)
diff --git a/mpvcore/av_common.h b/mpvcore/av_common.h
index 683570971d..103185329c 100644
--- a/mpvcore/av_common.h
+++ b/mpvcore/av_common.h
@@ -26,7 +26,7 @@ struct demux_packet;
 
 void mp_copy_lav_codec_headers(AVCodecContext *avctx, AVCodecContext *st);
 void mp_set_av_packet(AVPacket *dst, struct demux_packet *mpkt);
-double mp_get_av_frame_pkt_pdts(AVFrame *frame);
+void mp_get_av_frame_pkt_ts(AVFrame *frame, double *out_pts, double *out_dts);
 void mp_add_lavc_decoders(struct mp_decoder_list *list, enum AVMediaType type);
 int mp_codec_to_av_codec_id(const char *codec);
 const char *mp_codec_from_av_codec_id(int codec_id);