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List:       mjpeg-users
Subject:    Re: [Mjpeg-users] cvs mpeg2enc chokes on smil2yuv out
From:       "Steven M. Schultz" <sms () 2BSD ! COM>
Date:       2006-07-24 22:46:11
Message-ID: Pine.BSI.4.05L.10607241526390.29398-100000 () moe ! 2bsd ! com
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On Sun, 23 Jul 2006, sean wrote:

> I have a raw dv file.

> smil2yuv -i 2 test.dv > test.yuv

	Ok - so that decoded the DV data to a 4:1:1 Y'CbCr file (or as it's
	commonly called "yuv 411").

> cat test.yuv | mpeg2enc -f 8 -o test.m2v
> **ERROR: [mpeg2enc] Could not read YUV4MPEG2 header: stream 
> requires unsupported features!

	Which of course won't work since mpeg2enc accepts ONLY "yuv" (Y'CbCr)
	data that uses 4:2:0 sampling.  More properly "4:2:0 MPEG-2".

> head test.yuv
> YUV4MPEG2 W720 H480 F30000:1001 Ib A10:11 C411
                                              ^
					      |
					      Chroma sampling is 4:1:1

	MPEG does NOT allow 4:1:1.  MPEG-2 allows, at the main level/profile
	ONLY 4:2:0 (there is a 4:2:2 MPEG profile for professional/studio
	use but relatively few encoders support it).

> Should I be using something else to convert raw to yuv??

	I'll point out that the 'container' doesn't matter at all.  The DV
	data could be in a Quicktime file or in a type 2 AVI file and the
	error would be the same.

	DV data does use the "yuv" colorspace (for NTSC it's 4:1:1, for PAL
	it's 4:2:0PALDV).  It should also me mentioned that "yuv" has many
	forms - 4:1:1, 4:2:0, 4:2:2, 4:4:4, and I've seen a 3:1:1 mentioned
	once.  So to talk about converting to "yuv" is vague.

	a better and more accurate statement of the question would be:

	   How do I convert a file containing DV data to 4:2:0mpeg2 (something
	   mpeg2enc understands)?

	That can be answered.  You need to resample (convert) the chroma
	from 4:1:1 to 4:2:0.  This is done with y4mscaler.  y4mscaler can be
	found at http://www.mir.com/DMG/Software/y4mscaler.html

	In its simplest chroma conversion mode the usage is trivial:

	   ... | y4mscaler -O chromass=420mpeg2 | ...

	smil2yuv -i 2 test.dv | \
	    y4mscaler -O chromass=420mpeg2 | \
	    mpeg2enc -f 8 ...

	Cheers,
	Steven Schultz


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