demux, vd_ffmpeg: fix demux keyframe flag, set AV_PKT_FLAG_KEY

There was some confusion about the "flags" field in demuxer packets.
Demuxers set it to either 1 or 0x10 to indicate a keyframe (and the
field was not used to indicate anything else). This didn't cause
visible problems because nothing read the value. Replace the "flags"
field with a boolean "keyframe" field. Set AV_PKT_FLAG_KEY based on
this field in packets fed to libavcodec video decoders (looks like PNG
and ZeroCodec are the only ones which depend on values from demuxer;
previously this was hardcoded to true for PNG).

Make demux_mf set the keyframe field in every packet. This matters for
PNG files now that the demuxer flag is forwarded to libavcodec.

Fix logic setting the field in demux_mkv. It had probably not been
updated when adding SimpleBlock support. This probably makes no
difference for any current practical use.

1 files changed, 4 insertions, 2 deletions

diff --git a/libmpcodecs/vd_ffmpeg.c b/libmpcodecs/vd_ffmpeg.c
index b34b5b5593..b49b3c6975 100644
--- a/libmpcodecs/vd_ffmpeg.c
+++ b/libmpcodecs/vd_ffmpeg.c
@@ -642,8 +642,10 @@ static struct mp_image *decode(struct sh_video *sh, struct demux_packet *packet,
     av_init_packet(&pkt);
     pkt.data = data;
     pkt.size = len;
-    // HACK: make PNGs decode normally instead of as CorePNG delta frames
-    pkt.flags = AV_PKT_FLAG_KEY;
+    /* Some codecs (ZeroCodec, some cases of PNG) may want keyframe info
+     * from demuxer. */
+    if (packet && packet->keyframe)
+        pkt.flags |= AV_PKT_FLAG_KEY;
     if (packet && packet->avpacket) {
         pkt.side_data = packet->avpacket->side_data;
         pkt.side_data_elems = packet->avpacket->side_data_elems;