[Ffmpeg-devel] [RFC] Musepack seeking patch
Kostya
kostya.shishkov
Wed Dec 27 05:28:55 CET 2006
Here is a patch which enables full Musepack seeking.
As a side note: seeking may cause sound distortions because
Musepack stores scaling coefficients as difference to the
previous ones. libmppdec workarounds this by decoding
32 previous frames but that's a nasty hack and could not
be done here.
-------------- next part --------------
Index: libavformat/mpc.c
===================================================================
--- libavformat/mpc.c (revision 7375)
+++ libavformat/mpc.c (working copy)
@@ -71,6 +71,7 @@
c->curframe = 0;
c->lastframe = -1;
c->curbits = 8;
+ c->frames_noted = 0;
st = av_new_stream(s, 0);
if (!st)
@@ -156,15 +157,42 @@
return 0;
}
+/**
+ * Seek to the given position
+ * If position is unknown but is within the limits of file
+ * then packets are skipped unless desired position is reached
+ *
+ * Also this function makes use of the fact that timestamp == frameno
+ */
static int mpc_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
{
AVStream *st = s->streams[stream_index];
MPCContext *c = s->priv_data;
+ AVPacket pkt1, *pkt = &pkt1;
+ int ret;
int index = av_index_search_timestamp(st, timestamp, flags);
- if (index < 0)
+ uint32_t lastframe;
+
+ /* if found, seek there */
+ if (index >= 0){
+ c->curframe = st->index_entries[index].pos;
+ return 0;
+ }
+ /* if timestamp is out of bounds, return error */
+ if(timestamp < 0 || timestamp >= c->fcount)
return -1;
- c->curframe = st->index_entries[index].pos;
-
+ /* seek to the furthest known position and read packets until
+ we reach desired position */
+ lastframe = c->curframe;
+ if(c->frames_noted) c->curframe = c->frames_noted - 1;
+ while(c->curframe < timestamp){
+ ret = av_read_frame(s, pkt);
+ if (ret < 0){
+ c->curframe = lastframe;
+ return -1;
+ }
+ av_free_packet(pkt);
+ }
return 0;
}
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