demux_lavf: hack-fix EDL mp4 DASH hack

I encountered a stream that fails with "Could not demux init fragment.".
It turns out this is a regression from the recent change to that code.
The assumption was that demux_lavf.c would treat this as concatenated
stream - which it does, but not for probing.

Doing this transparently is hard without doing it properly. Doing it
properly would mean creating some sort of stream_concat (reminiscent of
that FFmpeg security bug). I probably don't want to go there, and I
think libavformat should just support this directly, so whatever.
Hack-fix this with the knowledge that the init segment will always
contain the headers.

(cherry picked from commit 315004a38a1bf9394507d8ca308da1ce86ca2204)

1 files changed, 4 insertions, 0 deletions

diff --git a/demux/demux_lavf.c b/demux/demux_lavf.c
index ee3918318a..8603a6a634 100644
--- a/demux/demux_lavf.c
+++ b/demux/demux_lavf.c
@@ -430,6 +430,10 @@ static int lavf_check_file(demuxer_t *demuxer, enum demux_check check)
             int nsize = av_clip(avpd.buf_size * 2, INITIAL_PROBE_SIZE,
                                 PROBE_BUF_SIZE);
             bstr buf = stream_peek(s, nsize);
+            if (demuxer->params && demuxer->params->init_fragment.len) {
+                buf = demuxer->params->init_fragment;
+                buf.len = MPMIN(buf.len, nsize);
+            }
             if (buf.len <= avpd.buf_size)
                 final_probe = true;
             memcpy(avpd.buf, buf.start, buf.len);