For the last couple of years, I had settled on using:
I found some spare time, so I'll show you how to do it -- the
relevant information up to now is kinda sketchy (to put it mildly
:‑) However, I will only describe the crux of it, and no, please
don't start asking me stuff. This is only for people who have a
working knowledge of both UNIX and video matters, so if you don't
know what an aspect ratio is, or why 0.2 bits per pixel is the
lowest limit of acceptable MPEG4 quality, stop reading this now
(while you're ahead :‑).
Sorry, but making a living writing software takes almost all of my time.
P.S. You 'll also get a Perl script to assist the work.
We'll tackle a rather advanced example, transcoding an NTSC telecined Dolby trailer, called dolby-city.vob. You can google the filename, it will immediately show up. Its rather big for plain modems though (27MB), so you can try to follow through these instructions with your preferred VOB anyway.
Naturally, if you want to encode DVD data, you'll have to store the unencrypted MPEG2 data somewhere; I'm assuming you know how to circumvent the CSS encryption to get to the MPEG2 data you want. mplayer -dumpstream dvd://1 can lead to legal troubles in certain countries, so make sure you are not breaking any laws doing it...
Most of what follows is automated through a Perl script I
made, but since you are reading this I'm guessing you want to
know the details :‑)
Click here to skip explanations and just use the script.
Let's assume that your MPEG2 data are stored in a directory called video:
heaven:/var/tmp/video$ ls -l -rw-r--r-- 2 ttsiod users 27963392 2005-02-07 19:44 dolby-city.vob
heaven:/var/tmp/video$ mkdir tmp heaven:/var/tmp/video$ mkfifo tmp/fifo heaven:/var/tmp/video$ tcscan -x pcm -i tmp/fifo & heaven:/var/tmp/video$ mplayer \ -ao pcm:nowaveheader:file=tmp/fifo \ -vo null -vc dummy -benchmark dolby-city.vob \ >/dev/null 2>&1This will output something like:
.. audio frames=849.60, estimated clip length=33.98 seconds .. (min/max) amplitude=(-0.252/0.274), suggested rescale=3.655 ..tcscan provides the normalization factor we need for our audio encoding process: usually, DVD audio has quite a dynamic range, so it needs some boosting for our transcoding. Now that tcscan has given us what we need, we'll encode the audio, normalizing it in the process.
Since a volume rescale of 3.655 is 20*log10(3.655) db, we...
heaven:/var/tmp/video$ echo '20*l(3.655)/l(10)' | bc -l 11.25774762587758519458 heaven:/var/tmp/video$ oggenc -b 64 -o audio.ogg tmp/fifo & heaven:/var/tmp/video$ mplayer -af volume=11.257747 -ao \ pcm:file=tmp/fifo -vo null \ -vc dummy -benchmark dolby-city.vob >/dev/null 2>&1(you can also try "-q 0" instead of "-b 64" - Vorbis audio is quite good even in 64kbps, and we'll use just that in this test).
The audio part is now done (in a more or less optimal way, in
terms of quality/bitrate).
Now the hard part: video.
Video can be a pain in the neck. Before we even get to the encoding part, we need to clear it up.
heaven:/var/tmp/video$ mplayer -vf cropdetect -nosound \ dolby-city.vobNavigate in the movie through the cursor/PgUp/PgDn keys to make sure you've fed the filter all it needs to see from your movie. In the end, abort mplayer and check the output for the last of the "crop area" lines:
crop area: X: 4..715 Y: 0..479 (-vf crop=704:464:8:8)Crop settings are now known: -vf crop=704:464:8:8. Test them:
heaven:/var/tmp/video$ mplayer -vf crop=704:464:8:8 \ -nosound dolby-city.vob
heaven:/var/tmp/video$ mplayer -vf pp=lb ...or, if its an NTSC telecined one, with
heaven:/var/tmp/video$ mplayer -vf detc -ofps 23.976 ...The latter one is the one you need for the dolby-city trailer. It is a telecined beast, so it needs one heck of a filter to get back to progressive.
Mencoder's documentation suggests against this; the authors feel that frame scaling is too much tampering with the original video, and that this is bad. They are over-reacting; we are doing this to squeeze more data in less storage, and doing this at the extreme level we want to simply REQUIRES scaling (unless we are targeting video bitrates more than 1MBit/sec, but then, why bother with H264 and not stick to MPEG4?)
To cut a very long story short, it was pointless to encode with MPEG4 - i.e. XVID, DIVX, or ffmpeg - to bitrates less than 0.2 bits per pixel. With H264, this changes: we can go lower, e.g. 0.125 bits per pixel and still get acceptable quality.
In dolby-city.vob, the original frame size is 720x480 pixels, at a (progressive, after deinterlacing) frame rate of 23.976 fps. This means that we would need at least
720 x 480 x 23,976 x 0,125 = 1035763,2 bits per second... if we were to avoid scaling. This bitrate is too high, we can't even fit a 2 hour movie in a 700MB CD with this rate.
512 x 384 x 23,976 x 0,125 = 589234,176 bits per secondNotice that at this bitrate, we would be able to fit 2.5 hours of movie time in one 700MB CD, since
Duration in seconds = 2,5*3600 = 9000 seconds Expected video size = 9000*589234,176/8 = 632 MBytes Expected audio size = 9000*64000/8 = 68 MBytes...which would fit nicely in our 700MB target size (thanks to Matroska's near zero cost multiplexing).
The reason we are first cropping, then deinterlacing and
finally scaling, should be obvious.
We can now complete the sequence with the H264 encoding parameters.
I won't bother explaining why you should always use two passes, just read the relevant info (or trust me):
mencoder -nosound -ofps 23.976 \ -vf crop=704:464:8:8,detc,scale=512:384 \ dolby-city.vob \ -o /dev/null -ovc x264 -x264encopts pass=1:bitrate=589Pass 2:
mencoder -nosound -ofps 23.976 \ -vf crop=704:464:8:8,detc,scale=512:384 \ dolby-city.vob \ -o video.avi -ovc x264 -x264encopts pass=2:bitrate=589Check video.avi; it has no sound, but video quality at this bitrate is simply beyond any comparison with MPEG4.
mkvmerge --engage allow_avc_in_vfw_mode -o Perfect.mkv \ video.avi audio.oggYou might need to synchronize video and audio; check the manpage for mkvmerge and learn how to use the -y switch. Or better yet, use the script: it utilizes mencoder in a way that guarantees video and audio will be in sync.
That's why I coded a very simple Perl script that glues
together all that you've seen.
Download it here and use it like this: (Update, August 2007: Thanks to Benjamin Pineau, if you are using the latest versions of mplayer and mkvmerge, you can download a patch here to support them)
heaven:/var/tmp/video$ vobs2mkv.pl dolby-city.vob 3 Perfect.mkv...which requests an encoding of the dolby-city.vob movie, and a generation of file Perfect.mkv with a size around 3 MBytes.
It also attempts to rip any MPEG2 subtitles existing in the stream to VOBSUB files, thus allowing a "perfect" rip; optimal video/audio/subtitle encoding.
This is the output (including the answers I gave) for 'dolby-city.vob':
Successfully located mplayer Successfully located mencoder Successfully located tcscan Successfully located mpegdemux Successfully located oggenc Successfully located ogginfo Successfully located mkvmerge Available audio channels: 1. 128 Automatically choosing audio channel 128 What codec should I utilize: 1. XVID 2. X264 Choose: 2 Identified Video stream successfully Identified AID 0x80 successfully Will now spawn mplayer to detect subtitle streams... Navigate with PgUp/PgDown to movie parts with subtitles... Hit ENTER when ready... and ESC to quit movie playback... No subtitles detected. Detected movie length of 35 seconds. Will now spawn mplayer to detect crop settings... Use the DOT key (.) to check for interlacing also... Hit ENTER when ready... ~/.mplayer/subfont.ttf doesn't look like a font description, ignoring. Cannot load font: /root/.mplayer/subfont.ttf The selected video_out device is incompatible with this codec. Try adding the scale filter, e.g. -vf spp,scale instead of -vf spp. Do you want the codec to encode as interlaced (Y/N) ? n Do you need NTSC inverse telecine (Y/N) ? y Expected Video bitrate: 620000 bits per sec MPEG2 Aspect Ratio: 1.33 FPS: 23.976 1. 208 x 160 (0.777019006185673) 2. 224 x 176 (0.655925135091802) ... 15. 496 x 384 (0.135769450005561) 16. 528 x 400 (0.12243935855047) ... Choose a number (1 - 18) : 16 Will now spawn mplayer so that you can check your frame settings Press ENTER when ready... Did you like your frame settings (Y/N) ? y Scaning to find amplification factor... Please wait... Audio will be scaled by 3.655 (11.2577 db). Encoding to Ogg Vorbis 96KBits/sec... ...After a couple of minutes, you'll get your Perfect.mkv.
You can have a look at what happened from tmp/log.txt:
heaven:/var/tmp/video$ cat tmp/log.txt 03:07:13 : mplayer -v -frames 0 dolby-city.vob 2>&1 | 03:07:15 : Encoding session starts 03:07:15 : dd if=dolby-city.vob bs=1M count=2 2>/dev/null | \ mpegdemux -c| 03:07:16 : mplayer -sid 0 -v -quiet dolby-city.vob 2>/dev/null | 03:07:16 : mencoder -ovc copy -nosound -o /dev/null \ -frameno-file /dev/null \ dolby-city.vob 2>/dev/null | 03:07:17 : mplayer -nosound -benchmark -vf cropdetect \ -quiet dolby-city.vob | 03:07:26 : mplayer -nosound -frames 10 dolby-city.vob 2>&1 | 03:07:47 : mplayer -nosound -really-quiet \ -vf crop=704:480:8:0,detc,scale=528:400 \ dolby-city.vob >/dev/null 2>&1 03:07:48 : mv tmp/videoCropDeinterAndScale \ tmp/videoCropDeinterAndScale.old 03:07:48 : rm -f tmp/fifo 03:07:48 : mkfifo tmp/fifo 03:07:48 : mplayer -really-quiet -aid 128 \ -ao pcm:file=tmp/fifo:nowaveheader -vo null \ c dummy dolby-city.vob >/dev/null 2>&1 & 03:07:48 : tcscan -i tmp/fifo -x pcm 2>/dev/null | 03:07:49 : mplayer -really-quiet -aid 128 -af volume=11.2577 \ o pcm:file=tmp/fifo -vo null -vc dummy dolby-city.vob \ dev/null 2>&1 & 03:07:49 : oggenc -s 123 -Q -b 96 -o tmp/audio.ogg tmp/fifo 03:07:52 : mencoder -ovc frameno -oac pcm -aid 128 -o \ frameno.avi dolby-city.vob 03:07:53 : ogginfo tmp/audio.ogg| 03:07:53 : mencoder -ofps 23.976 \ -vf crop=704:480:8:0,detc,scale=528:400 \ -ovc x264 -oac copy \ -x264encopts bitrate=654:pass=1:subq=6:\ 4x4mv:8x8dct:me=3:frameref=5:bframes=3:\ b_pyramid:weight_b \ -o /dev/null dolby-city.vob ...Enjoy!
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