From 907d7d972ada4eb4da59fd2db97442d2f865f270 Mon Sep 17 00:00:00 2001 From: Andreas Cadhalpun Date: Mon, 9 Mar 2015 14:59:44 +0100 Subject: [PATCH] ffmdec: limit the backward seek to the last resync position If resyncing leads to the same position as previously, it will again lead to a resync attempt, resulting in an infinite loop. Thus don't seek back beyond the last syncpoint. Signed-off-by: Andreas Cadhalpun Signed-off-by: Michael Niedermayer (cherry picked from commit 6b8263b03ab3d16d70525ae1893cb106be7852f1) Signed-off-by: Michael Niedermayer --- libavformat/ffmdec.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/libavformat/ffmdec.c b/libavformat/ffmdec.c index de11f8a006..09a76e5995 100644 --- a/libavformat/ffmdec.c +++ b/libavformat/ffmdec.c @@ -77,6 +77,7 @@ static int ffm_read_data(AVFormatContext *s, FFMContext *ffm = s->priv_data; AVIOContext *pb = s->pb; int len, fill_size, size1, frame_offset, id; + int64_t last_pos = -1; size1 = size; while (size > 0) { @@ -96,9 +97,11 @@ static int ffm_read_data(AVFormatContext *s, avio_seek(pb, tell, SEEK_SET); } id = avio_rb16(pb); /* PACKET_ID */ - if (id != PACKET_ID) + if (id != PACKET_ID) { if (ffm_resync(s, id) < 0) return -1; + last_pos = avio_tell(pb); + } fill_size = avio_rb16(pb); ffm->dts = avio_rb64(pb); frame_offset = avio_rb16(pb); @@ -112,7 +115,9 @@ static int ffm_read_data(AVFormatContext *s, if (!frame_offset) { /* This packet has no frame headers in it */ if (avio_tell(pb) >= ffm->packet_size * 3LL) { - avio_seek(pb, -ffm->packet_size * 2LL, SEEK_CUR); + int64_t seekback = FFMIN(ffm->packet_size * 2LL, avio_tell(pb) - last_pos); + seekback = FFMAX(seekback, 0); + avio_seek(pb, -seekback, SEEK_CUR); goto retry_read; } /* This is bad, we cannot find a valid frame header */