On 09.03.2015 13:59, Michael Niedermayer wrote:
i was thinking more about limiting the backward seek before resync
to the last resync position +1 if there was a previous resync
so that resync which moves forward could not end before. This would
avoid the failure and allow the demuxer to continue, or at least thats
the idea
I see, new patch attached.
The +1 is not necessary, because it always reads the PACKET_ID field
before resyncing.
Best regards,
Andreas
>From 6bcd1b4a906e2da39f6361db19826a337ac5a745 Mon Sep 17 00:00:00 2001
From: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
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 <andreas.cadhal...@googlemail.com>
---
libavformat/ffmdec.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/libavformat/ffmdec.c b/libavformat/ffmdec.c
index fc43668..ec91b6f 100644
--- a/libavformat/ffmdec.c
+++ b/libavformat/ffmdec.c
@@ -79,6 +79,7 @@ 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) {
@@ -98,9 +99,11 @@ 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);
@@ -114,7 +117,9 @@ 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 */
--
2.1.4
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