On Sat, 17 Jul 2004, Glenn Morse wrote:
> Hello, I'm having some trouble with mpeg2enc giving me an error I don't
> understand...
> glenn DVD $ jpeg2yuv -n 50 -I p -f 29.97 -j tmp/out-1.jpg | mpeg2enc -n
> n -f 8 -o tmp/background.m2v
...
> INFO: [jpeg2yuv] Processing non-interlaced/interleaved
> tmp/out-1.jpg, size 14221l.
> INFO: [mpeg2enc] Selecting DVD output profile
> ++ WARN: [mpeg2enc] No aspect ratio specifed and no guess possible:
> assuming 4:3 display aspect!
> INFO: [mpeg2enc] Progressive input - selecting progressive encoding.
> INFO: [mpeg2enc] Encoding MPEG-2 video to tmp/background.m2v
> INFO: [mpeg2enc] Horizontal size: 720 pel
> INFO: [mpeg2enc] Vertical size: 576 pel
> INFO: [mpeg2enc] Aspect ratio code: 2 = 4:3 display
> INFO: [mpeg2enc] Frame rate code: 4 = 30000.0/1001.0 (NTSC VIDEO)
> INFO: [mpeg2enc] Bitrate: 7500 KBit/s
> **ERROR: [mpeg2enc] Sample rate is greater than permitted in specified Level
>
> What exactly does "Sample rate is greater than permitted in specified
> level" mean? How can I correct this?
It means a couple things. One thing is that the error message is
slightly phrased - it should have said "frame size" instead of
"sample rate".
But mostly it means you specified NTSC (the "-n n") to mpeg2enc but
then went and fed as input a PAL frame size.
For NTSC the maximum framesize for [EMAIL PROTECTED] (Main Profile @ Mail
Level)
is 720x480. Thus 720x576 is out of range.
Why did you create a 720x576 image instead of a 720x540? 720/540 is
a 4:3 image where 720x576 is not.
Or are you in a PAL country?
The other (warning) error is also a clue that things are not set up
right for what you're trying to do.
The message "No aspect ratio specified ..." means that 'jpeg2yuv' is
generating a sample aspect ('A') tag of 0:0 meaning unknown. If you do
something like this:
jpeg2yuv -n 50 -I p -f 29.97 -j file.jpg | head -n 1
I wager you will see something like this:
YUV4MPEG2 W720 H576 F30000:1001 Ip A0:0 C420jpeg
mpeg2enc uses the framesize and sample aspect ratio (SAR) to try and
figure out the display aspect ratio (DAR). A0:0 means "unknown" and
that is what mpeg2enc is warning about before defaulting to 4:3 for
the DAR. Arguably jpeg2yuv should use "A1:1" since computer generated
graphics are often/mostly square pixels.
What you need to do is resample/scale the data to 720x480 Rec.601
pixels which for NTSC have an aspect of 10:11.
y4mscaler (http://www.mir.com/DMG/Software/y4mscaler.html) will do
that extremely accurately. Oh. while you are doing that it's probably
also a good idea to convert the chroma from 420JPEG to 420MPEG2. Again,
y4mscaler to the rescue!
Something like this should do the job:
jpeg2yuv ... | \
y4mscaler -I sar=1:1 -O sar=10:11 -O size=720x480 -O chromass=420_mpeg2 | \
mpeg2enc ...
Actually that's probably not exactly right for a 720x576 image.
If you're doing computer generated graphics for encoding you generate
them at the intended Display Aspect (4:3 or 16:9). For NTSC that
works out to 720x540 and 854x480 respectively. Then you scale the image
to the DVD frame size of 720x480.
Have fun!
Cheers,
Steven Schultz
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