[MPlayer-dev-eng] problem in nuv demuxer?

[D Richard Felker III]

After experimenting with tons of live tv capture programs, the only
one I've found that remotely works is NuppelVideo's nuvrec. However,
with -r (raw) it takes way too much disk space (not to mention disk
bandwidth) to be usable, and the output of the RTjpeg codec is hideous
even with -Q 255 -- certainly not suitable for reencoding with mpeg4.
So, I tried the following experiment:

mkfifo test.nuv
nuvrec -n -S 1 -W 320 -H 240 -r test

mencoder test.nuv -oac pcm -lavcopts vcodec=mjpeg:vqscale=2

Capturing like this works beautifully for ten seconds or so, but then
mencoder always seems to crash. The problem seems to be that
ds_read_packet is allocating a packet of length 0 and then trying to
memcpy to its buffer. The crash is in an inline function from
stream.h:

141         memcpy(mem,&s->buffer[s->buf_pos],x);

I imagine the problem is that the nuv demuxer doesn't know how to deal
with the case where it only reads a partial packet because the rest
hasn't made it through the pipe yet, but this is just a guess.

Apologies for posting this to the dev list if it's inappropriate (let
me know if that's the case). I'm interested in helping to fix this
though, if I can figure out how all this stuff works, so I figure it's
at least somewhat relevant here.


Rich

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brightrain:~$ gdb ~/src/mplayer/mencoder
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This GDB was configured as "i586-pc-linux-gnu"...
(gdb) run test.nuv -oac pcm -lavcopts vcodec=mjpeg:vqscale=2
Starting program: /home/dalias/src/mplayer/mencoder test.nuv -oac pcm -lavcopts vcodec=mjpeg:vqscale=2


MEncoder CVS-020713-20:27-2.95.3 (C) 2000-2002 Arpad Gereoffy (see DOCS!)

CPU: Advanced Micro Devices K6-2 (Family: 5, Stepping: 12)
CPUflags: Type: 5 MMX: 1 MMX2: 0 3DNow: 1 3DNow2: 0 SSE: 0 SSE2: 0
Reading /home/dalias/.mplayer/codecs.conf: can't open '/home/dalias/.mplayer/codecs.conf': No such file or directory
Reading /usr/local/share/mplayer/codecs.conf: 36 audio & 103 video codecs
File not found: 'frameno.avi'
/home/dalias/.mplayer/mencoder(1): option: ni
/home/dalias/.mplayer/mencoder(1): parameter: 1
/home/dalias/.mplayer/mencoder(2): option: lavcopts
/home/dalias/.mplayer/mencoder(2): parameter: vcodec=mpeg4:vqmin=2:vrc_strategy=1
/home/dalias/.mplayer/mencoder(3): option: lameopts
/home/dalias/.mplayer/mencoder(3): parameter: aq=2
/home/dalias/.mplayer/mencoder(4): option: tv
/home/dalias/.mplayer/mencoder(4): parameter: chanlist=us-bcast:norm=ntsc:driver=v4l:input=1:width=320:height=240:outfmt=i420
font: can't open file: /home/dalias/.mplayer/font/font.desc
Font /usr/local/share/mplayer/font/font.desc loaded successfully! (206 chars)
success: format: 0  data: 0x0 - 0x0
Detected NuppelVideo file format!
[V] filefmt:13  fourcc:0x3156554E  size:320x240  fps:29.97  ftime:=0.0334
Detected audio codec: [pcm] drv:2 (Uncompressed PCM)
Opening audio decoder: [pcm] Uncompressed PCM audio decoder
AUDIO: srate=44100  chans=2  bps=2  sfmt=0x10  ratio: 176400->176400
libavcodec: CPU flags: mmx 3dnow
Opening video filter: [expand=-1:-1:-1:-1:1]
Expand: -1 x -1, -1 ; -1  (-1=autodetect) osd: 1
==========================================================================
Opening video decoder: [nuv] NuppelVideo decoder
VDec: vo config request - 320 x 240 (preferred csp: Planar I420)
Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
videocodec: libavcodec (320x240 fourcc=47504a4d [MJPG])
Using constant qscale = 2 (VBR)
Detected video codec: [nuv] drv:15 (NuppelVideo)
==========================================================================
CBR PCM audio selected
Writing AVI header...
Pos:   0.7s     22f ( 0%)   9fps Trem:   0min   0mb  A-V:-0.070 [0:1411]
duplicate 1 frame(s)!!!
Pos:   1.1s     33f ( 0%)  11fps Trem:   0min   0mb  A-V:-0.068 [6255:1411]
duplicate 1 frame(s)!!!
Pos:  11.5s    343f ( 0%)  25fps Trem:   0min   0mb  A-V:-0.053 [6577:1411]
Program received signal SIGSEGV, Segmentation fault.
0x401cee97 in memcpy () from /lib/libc.so.6
(gdb) bt
#0  0x401cee97 in memcpy () from /lib/libc.so.6
#1  0x80f58d2 in ds_read_packet (ds=0x824b570, stream=0x8249420, len=522266171, pts=874913.312, pos=42752316, flags=0)
    at ../libmpdemux/stream.h:141
#2  0x81050fc in demux_nuv_fill_buffer (demuxer=0x824aca0) at demux_nuv.c:176
#3  0x80f5af9 in demux_fill_buffer (demux=0x824aca0, ds=0x824b508) at demuxer.c:283
#4  0x80f5d21 in ds_fill_buffer (ds=0x824b508) at demuxer.c:342
#5  0x80f5dc6 in demux_read_data (ds=0x824b508, mem=0x82723a0 "?", len=65536) at demuxer.c:361
#6  0x8063e18 in decode_audio (sh_audio=0x824b718, buf=0x82723a0 "?", minlen=65536, maxlen=67584) at ad_pcm.c:69
#7  0x8061f14 in decode_audio (sh_audio=0x824b718, buf=0x82723a0 "?", minlen=65536, maxlen=67584) at dec_audio.c:130
#8  0x804b294 in dec_audio (sh_audio=0x824b718,
    buffer=0x40725008 "?\a\\\006\223\au\006L\ah\006\031\a%\006?\006?\005\227\006?\005\e\006?\005\215\005\202\005\r\005;\005\234\004?\0046\004\237\004\006\004h\004?\003O\004\037\004+\004\177\004\013\004?\004\005\004;\005\034\004~\005,\004?\005\013\004\236\005?\003{\005?\003c\005\216\0035\005I\003?\004?\002?\003h\002-\003?\001?\002f\001\234\002?", total=88200) at mencoder.c:262
#9  0x804cbe1 in main (argc=6, argv=0xbffffc04, envp=0xbffffc20) at mencoder.c:878
(gdb)