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lav2wav(1)		      MJPEG tools manual		    lav2wav(1)

       lav2wav - Extract the audio out of MJPEG	container files	to stdout

       lav2wav	[-s num] [-c num] [-v num] [-I]	[-R] [-r samplerate, bitesize,
       channels] lavfile1 [lavfile2 ...	lavfileN]

       lav2wav can be used to extract the audio	to stdout.  This  output  goes
       to stdout and can be saved as a wav file	or piped to another sound pro-
       cessing tool that is able to handle the wav format.  This can be	mp2enc
       and  toolame for	mpeg layer 2 audio, or for example lame	for mpeg layer
       3 audio.

       The input files may be any combination of AVI (.avi),  Quicktime	 (.qt)
       or  editlist  files  so	long  as they are all lavtools-	readable (e.g.
       MJPEG-encoded AVI/Quicktime or DV type 2	AVI).

       lav2wav accepts the following options:

       -s num
	    Start extracting at	video frame (num)

       -c num
	    Extract (num) frames of audio

       -v num
	    Verbosity level (0,	1 or 2)

       -I   Ignore unsupported bitrates/bits per sample

       -R   If the file	does not contain any sound. lav2wav  will  create  si-
	    lence with 44100kHz	Sampelrate, 16 Bit audio bitsize and 2 Chanels

       -r sr,bs,ch
	    If	the  file does not contain any sound lav2wav will generate si-
	    lence with the values you supply the samplerate  (sr),  audio-bit-
	    size (bs) and channel (ch).

       The "WAV" file format (technically: RIFF) is really very	much less than
       ideal for a tool	intended to be used in pipelines as lav2wav  is.   The
       problem	is  that  the header includes a	field specifying the length of
       the file.  This can't be	filled in except by seeking back to the	begin-
       ing  and	over-writing.  If the output is	unseekable (e.g. pipe) lav2wav
       simply writes a large length into the header and	 leaves	 it  at	 that.
       Most tools like sox(1) or mp2enc(1) either ignore the length field any-
       way or only give	a warning.
       The audio length	is inacurate calculated	 when  lav2wav	generates  si-
       lence.	This  happens only if you have NTSC framerate and than it cre-
       ates for	every hour of video 1.1498sec too less of silence.

       This man	page was written by Bernhard Praschinger.
       If you have questions, remarks, problems	or you just  want  to  contact
       the developers, the main	mailing	list for the MJPEG-tools is:

       For more	info, see our website at

       mjpegtools(1), mp2enc(1), sox(1)

MJPEG Tools Team		  2 June 2001			    lav2wav(1)


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