On Thu, 23 Dec 2004, Dave Dodge wrote:
> I want to _generate_ HD output; ideally an ATSC-compliant TS but a
> 720p30 video ES would be a good start. I have my animation/rendering
I know the ABC network (and I think FOX) are using the 720p but it's
60 frames/sec not 30 (well, ok - 60000/1001 ;))
> program configured to produce 1280x720 PPM frames at 30 frames per
> second.
30fps is a valid ATSC rate (as is 30000/1001)
> see any glaring problems with these settings? I've kept all of the
What you're going to run into when trying to work with HD output is
that 'mpeg2enc' is a [EMAIL PROTECTED] (Main Profile @ Main Level)
encoder and
not a HL (High Level) encoder. While "--intra_dc_prec 11" ("-D 11")
_appears_ available it falls into the same category as "-F 6" (50
frame/sec) thru "-F 8" (60 frames/sec) - it doesn't really work.
> cat *.ppm \
> | ppmtoy4m -n 150 -F 30:1 -A 1:1 -I p -S 420_mpeg2 \
> | mpeg2enc \
> --no-constraints \
> --format 3 \
> --b-per-refframe 0 \
> --video-bitrate 19000 \
> --video-buffer 500 \
> --no-dummy-svcd-SOF \
> --min-gop-size 15 \
> --max-gop-size 15 \
> --closed-gop \
> --keep-hf \
> --intra_dc_prec 11 \
> --output outputfile.mpg
>
> With the above settings I found that mjpegtools-1.6.2 initially
> complained about the bitrate and/or dc precision being out of range.
Upgrade to the cvs version if you're going to try and do anything
with HD content. It's possible to cajole mpeg2enc into doing the
above but there was a bug in 1.6.2 - basically the "--no-constraints"
didn't work (did not have the desired effect(s)).
"-D 10" (--intra_dc_prec 10) should work fine - I don't know if the
11bit has ever been tested (since it's not allowed with [EMAIL
PROTECTED] MPEG-2).
> Is there any way to select the high level and high profile settings on
> the command line? I couldn't find any and ended up patching the
You won't be able to use -F6 thru 8 but if you use the CVS version
the higher bitrate and framesize can be (with --no-constraints) be
made to work.
> I suspect the bitrate might be too high if I want to stay within the
> bounds of broadcast ATSC, since packetization will add overhead. But
Most of the HD stations I watch are the [EMAIL PROTECTED]/1001 format.
(the stream is actually 1920x1088 since 1088 is a multiple of 16 and
the 'vertical display size' field of the mpeg2 header is set to 1080 -
I've requested that the ability to set the 'vertical display size'
be added to mpeg2enc).
To continue on... ;) The stations broadcast a SD and an HD program
at the same time - they use about 14Mb/s for the HD (with a 384Kb/s
5.1 AC3 audio track) and about 5Mb/s or so for the SD stream. 19Mb/s
should be ok but you might want to back down just a little to leave
room for the overhead. The VBV size I've seen used is 488 (which is
close to the 500 you've specified)
> it. There's not intended to be any audio associated with the video,
> so I don't think I need to leave any room for it.
Silent movie era in High Definition :)
To generate the TS stream you may want to give ProjectX a try - I use
that all the time to _de_mux TS streams (captured via IEEE1394 from
a tuner I have) but ProjectX also appears to be able to _create_
TS streams from elementary input files.
> on a TS). There seem to be several free programs to tear transport
> streams apart but very few for constructing them.
http://www.lucike.info/index.htm?http://www.lucike.info/page_projectx.htm
might be worth a try - runs nicely for demuxing (on both OS/X and
linux).
Cheers,
Steven Schultz
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