[mythtv-users] segfault in mythtranscode

[Mike Morrison]

Hi,

I'm getting a segfault in mythtranscode.  I'm not entirely sure that I'm
using it
correctly, but even if I'm not, it shouldn't segfault.  I'm using the
latest CVS
version of mythtv as of 4:25pm PDT July 14 2004.

All I want to do is to cut some commercials out of a video stream.  I'm
not really
interested in actually transcoding it.  I added some cutpoints to the
video stream,
and told it to begin transcoding.  It starts running and then after a
while segfaults.
I tried a couple of different video streams and got similar results.
I had a few IOBOUND Write (or something similar) messages in the
mythbackend output,
and I made those go away be recompling with 4M buffers in RingBuffer.cpp. 
Still
segfaults, though.  Recompiled with debugging.  Stacktrace below.  It
looks like
a memory corruption problem of some kind; 34 seems like a suspicious value
for
useavodec and mpa_codec points off into the weeds.

I never (well, at least not intentionally) setup any of the transcoder
profiles,
and I don't really know if I need to.  If it matters, the video stream is
a capture
of a 720p OTA HDTV signal.  It probably has some bit errors in it, though
nothing
severe.  Is it possible for a bad video stream to cause a crash?

Here's the stack trace from a manual run with the same command line
arguments
mythbackend uses:

(gdb) r -c 1003 -s 2004-07-11T20:30:00 -p autodetect -d -l
...<snip>...
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 1083875520 (LWP 3062)]
0x40354a8f in NuppelVideoRecorder::WriteVideo (this=0x40c0c008,
frame=0xbfffd550, skipsync=false, forcekey=false)
    at NuppelVideoRecorder.cpp:3346
3346            if (mpa_codec->id == CODEC_ID_RAWVIDEO)
(gdb) bt
#0  0x40354a8f in NuppelVideoRecorder::WriteVideo (this=0x40c0c008,
frame=0xbfffd550, skipsync=false, forcekey=false)
    at NuppelVideoRecorder.cpp:3346
#1  0x08057b75 in Transcode::TranscodeFile (this=0x8084198, 
    inputname=0x80880a0
"/data/video/1003_20040711203000_20040711210000.nuv", 
    outputname=0x8088260
"/data/video/1003_20040711203000_20040711210000.nuv.tmp", profileName=
      {static null = {static null = <same as static member of an already
seen type>, d = 0x8066070, static shared_null = 0x8066070}, d = 0x806a728,
static shared_null = 0x8066070}, honorCutList=true, framecontrol=false,
chkTranscodeDB=true, fifodir=
      {static null = {static null = <same as static member of an already
seen type>, d = 0x8066070, static shared_null = 0x8066070}, d = 0x806a740,
static shared_null = 0x8066070}) at transcode.cpp:563
#2  0x0804fd86 in main (argc=9, argv=0xbfffd914) at main.cpp:275
(gdb) p useavcodec
$1 = 34
(gdb) p mpa_codec->id
Cannot access memory at address 0xb8b9b61c

-- Mike




		
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