demux: always use AVPacket

This is a simplification, because it lets us use the AVPacket
functions, instead of handling the details manually.

It also allows the libavcodec rawvideo decoder to use reference
counting, so it doesn't have to memcpy() the full image data. The change
in av_common.c enables this.

This change is somewhat risky, because we rely on the following AVPacket
implementation details and assumptions:
- av_packet_ref() doesn't access the input padding, and just copies the
  data. By the API, AVPacket is always padded, and we violate this. The
  lavc implementation would have to go out of its way to make this a
  real problem, though.
- We hope that the way we make the AVPacket refcountable in av_common.c
  is actually supported API-usage. It's hard to tell whether it is.

Of course we still use our own "old" demux_packet struct, just so that
libav* API usage is somewhat isolated.

1 files changed, 2 insertions, 4 deletions

diff --git a/demux/packet.h b/demux/packet.h
index 21c0a6dc8f..9c4e560e05 100644
--- a/demux/packet.h
+++ b/demux/packet.h
@@ -34,13 +34,11 @@ typedef struct demux_packet {
     bool keyframe;
     int stream; // source stream index
     struct demux_packet *next;
-    void *allocation;
-    struct AVPacket *avpacket;   // original libavformat packet (demux_lavf)
+    struct AVPacket *avpacket;   // keep the buffer allocation
 } demux_packet_t;
 
 struct demux_packet *new_demux_packet(size_t len);
-// data must already have suitable padding
-struct demux_packet *new_demux_packet_fromdata(void *data, size_t len);
+struct demux_packet *new_demux_packet_from_avpacket(struct AVPacket *avpkt);
 struct demux_packet *new_demux_packet_from(void *data, size_t len);
 void demux_packet_shorten(struct demux_packet *dp, size_t len);
 void free_demux_packet(struct demux_packet *dp);