On Tue, 22 Jun 2004, Steven Ellis wrote:
> Ok first up sorry for the cross post. I read all these lists and I feel
I'm must posting the reply back to the mjpegtools list since 1) that's
the one where I have the most expertise/knowlege and 2) other than
ffmpeg is the only one I read.
> Now I know the graphics card is a little ancient but hey it works well
> enough for my editing.
A nVidia FX5200 is __cheap__ and comes with a MPEG_2 decoder than
MPlayer and ffmpeg know how to tap into. Quite useful for playback
even when the system is under heavy load (since the decoding is
shoved out to the graphics card).
> Requirements
> ------------
> Full screen D1 PAL Capture with 48000Hz Audio, to be transcoded into
> DVD. Zero frame drops or under 5 frames/hour. Accurate sync. Lossless,
> or close to lossless.
Ok - 100% doable. Except for the lossless part - that's not needed
as I hope you'll see.
> Tools - Capture
> ---------------
The solution I have in mind uses a rather different set of
tools but more on that in a bit...
> ffmpeg - Never happy with the level of control or the poor v4l2 support
It's mpeg-2 output has never struck me as being better than mpeg2enc's
and over time most of ffmpeg's much vaunted speed advantage seems
to have disappeared, at least on my G5/Altivec system.
> mencoder - Also strange v4l2 problems so I haven't used it in quite some
> time.
Good MPEG-4 encoding front end but that's about all - and even then
I find it necessary to use tools from mpeg4ip.sf.net to get things
into shape where Apple's Quicktime player will accept them...
> lavrec - Way too many frame drops. Don't understand why. Can someone
> give me some tips on how to best tweak this.
The solution I have in mind (which will completely satisfy the
no frame drop, etc requirements) doesn't use lavrec
> nvrec - Used this for quite a while, especially when some of the ffmpeg
Never used that one or ffv1rec.
> Tools - Editing/Tweaking
> ------------------------
> MPlayer - Together with mencoder. Great at tweaking/playing broken video
> streams.
I use MPlayer a lot to play files of all sorts - fantastic program.
> ffmpeg - Need I say more. Awesome guys
'bout the most I've used that for is libavcodec/ and libavformat/
to build MPlayer and a few other things. libavcodec/dv.c is a superb
DV decoder.
> The Issues
> ----------
> 1. The better quality codecs keep resulting in frame drops. Some due to
> CPU (FFV1 + LJPEG) others due to data rate (HUFFYUV).
So, and this may come as a shock/surprise: don't do the encoding at
capture time. Seriously - do the batch/bulk capture (disk space is
almost as cheap as dirt these days - 250GB drives going for $120 or
less if you keep an eye open for the sales). But more importantly
have hardware do the frontend compression (if any).
> 3. Current solutions (MJPEG / MPEG4 / XVID) have interlace video issues
> or dark area encoding problems.
Not to mention MPEG4 can't be placed on a DVD which I believe was
the stated goal.
> 4. No suitable real-time software MPEG2 solution at this stage.
Right, so, as the sign in the one restaurant says:
Good cooking takes time, if you are made to wait it is so that
we may serve you better.
I never had an interest in real time encoding anyhow - I need to
stack a few filters in the pipeline to get the quality of the picture
up (and VHS needs all the help it can get ). The MPEG-2 encoding
part of the run is actually the fastest part - the filters I insert
take more cpu time than the encoder does ;)
> 5. FFMPEG has a much quicker MPEG2 renderer than MJPEG Tools, but it
> still isn't quite standards compliant enough for my Philips DVD 711.
Not all that much quicker and the visual quality's never struck my
eyes as being as good but maybe it's gotten better since the last
time I tried it.
> Solutions ?
> -----------
> 1. Software equivalent to Current HW MPEG2 solutions. Capture at high
> bitrate MPEG2 and down convert/shrink later. As I want to do edits etc
> it would be a re-render and not a requant.
MPEG is a horrid format for editing - it can be made a little better
if you use short _closed_ GOPs but still it's a constant decode/recode
exercise and the quality will degrade at each step.
> 2. Speed up FFV1 support in FFMPEG? Or a suitable replacement.
Got just the thing in mind ;)
> 3. Better/quicker lossless MJPEG support
MJPEG is a lossy method - you can control the amount of loss but I
don't think it goes to 0. Unless you have a MJPEG capture card then
you have to do the jpeg compression in software.
> 4. Tweak hard drive performance for better huffy support.
Forget that too ;)
> Your Help?
> ----------
> So one and all feed back welcomed, and flames ignored. What are people
> using and just how fussy are you?
I consider myself fussy. My initial dabbling years ago was with a
Bt878 based capture card but a couple years back I went the DV/IEEE1394
route. Took a single 1 minute capture/encode session and the Bt878
card was _never_ used again. Others have also performed the DV
experiment and the reaction has always been the same - as in "oh my,
the quality's noticeably better". Perhaps the last chap who had
the ephiphany will chime in with his report.
Get yourself a IEEE1394 card (very cheap) and a Canopus ADVC100 or
even better (but somewhat more expensive) ADVC300 analog to DV
converter. The ADVC300 has a TBC and denoising capability built in
so it's well suited to convering VHS tapes which have less than great
picture stability/quality.
> I'm based in NZ so I don't have any DVB-T or DVB-S access to hand, and
> HW MPEG2 is silly prices (in NZ terms). I want a good analog capture
> system for off air and VHS conversions.
A analog<->DV converter is perfect for that. The data rate is a
fixed ~12GB/hour - the framesize is fixed which means that 'dd' can
be used as an emergency editor if the need should arise. DV has a
fixed 5->1 reduction in the raw (~124Mb/s) video rate - the video
part of DV is 25Mb/s and the audio's 1.5Mb/s (48kHz, 16bit).
No fussyness with capture sizes, etc - DV's 720x480 (or 720x576 PAL).
Period. Want smaller sizes then 'y4mscaler' can do the job after
the capture session.
No need for any fancy hard drive performance tweeking - there's not
a drive around that has trouble sustaining ~3.6MB/s (which includes
the 48kHz audio). I just did 3 hours of capturing tonight with 0
(0.00000) dropped frames. Oh, no A/V sync issues at all even when
editing since the Canopus unit has 'locked audio'.
Total of 32GB of data. Edited with kino and the encoding'll start in
a while (ftp the data up to the dual G5 system and let it grind away).
Use 'dvgrab' to capture, 'kino' to edit, and 'smilutils' to induct
the data into mpeg2enc (smil2yuv can be built with ffmpeg's DV
decoder - by default libdv's decoder is used).
I'm using a Canopus ADVC100 and one of those color correction/
stabilizer boxes - if I were doing it today I'd get a ADVC300 as
a higher quality setup. Cheap no-name IEEE1394 card. The Bt878
card's off in a static bag somewhere - haven't gotten around to
tossing it out yet ;)
A benefit of having a IEEE1394 card in the system is that you can
simply plug in your miniDV camcorder (if/when you get one) and use the
same tools that you've been creating DVDs with. Can also plugin
external disk drives. IEEE1394 card is a very useful thing to have
in a system.
No flames - but that's my contribution (and wow - was a bit verbose
wasn't it?).
Cheers,
Steven Schultz
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