[vmpaul]

This came up in another thread about EyeTV. That program records video in MPEG-1. An hour of video is around 650mgs.

If I converted that file using QuickTime into MPEG-4 video does anybody know what kind of compression I would get? How big would that file end up being?

I imagine that the speed would depend on processor but a rough estimate of time would be helpful as well. If anone has done this.

[C.J. Moof]

I just played with this a little today, and ran into some problems. I started with a VCD ready mpeg of Firefly, with the intention of moving it to MPEG4 so I could serve it via QTSS. My intention was to do a "proof of concept" if this would work, as my EyeTV should be here Monday- it's files should be just like this one.

Conversion on my 450Mhz Cube was maybe half realtime. I didn't time it, and I was suring, emailing, iTunes, all that good stuff OS X lets ya do while a major video transcode goes on in the background.

The MPEG went from 432Megs to 229. Unfortunately, there was one dealbreaker in there- I ended up without any audio, so a usable video will be somewhat bigger. When I looked at it again, I noticed that the export window says that no audio will be output because this has no audio tracks. Well, it does... I think this is an irritating quirk of multiplexed audio and video.

If moving these to mpeg4 requires re-encoding, demuxing audio, separately encoding that, and adding audio back to the mpeg4 file, forget it. I'll buy a stack of cheap CDs and burn VCD's first.

[vmpaul]

Wow, that's a bummer. Why does it have to be so difficult?

Compression sounds good but if it's without sound...

Thanks for the update. If you try anymore please post the results.

[C.J. Moof]

Originally posted by vmpaul:
Wow, that's a bummer. Why does it have to be so difficult?

Compression sounds good but if it's without sound...

Thanks for the update. If you try anymore please post the results.

Don't get too excited about that compression- there was definitely a loss of quality to get there. I used QT's Export for .mp4 with the options set to LAN, meaning it should have been on the upper range of quality.

Drives crash. CD's basically don't, they're cheap, and are easy to store. And they go in my DVD player.

[Uncle Skeleton]

1, MPEG export. Quicktime inexplicably treats muxed MPEG-1 and MPEG-2 tracks as one large sample (like how CD audio is 44100 samples per second, etc), except mp3 tracks which are still MPEG-1 but work fine. Therefore, to export the audio you need to demux the raw MPEG (be sure not to save it as a quicktime movie with an mpeg track first) with bbDemux, the audio product of which you can then convert with iTunes after changing the filename to end in .mp2

2, Apple's mpeg-4 codec. You can usually get much better quality by exporting to MOV, with mpeg-4 as the codec, choosing quality over speed as well as all the other mpeg-4 tricks like height/width multiples of 16 and no black or muddy edges, noise reduction, etc. Actually, to get better quality it would be best to use a better encoder like 3ivx, Xvid or DivX, but you're not going to like the steps necessary to mux an mp4 out of those if you're already complaining about muxing Apple mpeg-4...Anyway, back on track, if you have Apple branded mpeg-4 video and audio in MOV files you can open them in QTPro, copy, Add (edit menu), and export to mp4 with Passthrough for encoding.

3, Recompression. I don't think it's worth your time to recompress these files, unless you need to stream them over the internet. MPEG-1 is already significantly compressed (lossy), and it's always a bad idea to recompress a compressed source. As mentioned, you lose quality, you only get about 2x more compression, and the result won't play on a standalone player (not for a few years at least)

4, difficulty. Apple assumes (basically rightly) that MPEG-1 and MPEG-2 are delivery formats, not intermediate. Since it's rarely a good idea to re-encode from them anyway, they're not investing in improving the outdated behavior of QTPlayer, which was probably just an oversight anyway...I'm getting off track again....

[Chun Hsu]

vmpaul, I replied to the EyeTV thread on this topic, but I will add in a little bit here.

MPEG conversion is unfortunately a pain with Quicktime. The easiest way takes two steps:

- Use ffmpegX to convert MPEG1 to Divx AVI file.
- Convert AVI file to Quicktime using Divx Doctor.
- Enjoy!

You can download ffmpegX from version tracker. It's a wrapper around a free Unix utility to do all sorts of encoding. The only painful part is figuring out the options the first time. After that, it's not so bad. You can get Divx Doctor from the 3ivx web site. You will also need to install the 3ivx encoder so that Quicktime knows how to handle Divx. Encoding on a MDD DP 1Ghz is about real time. I could run two in parallel and still get real time since only 1 CPU is being used for each encoding. Running Divx Doctor just takes a couple of minutes.

I agree with most of Uncle Skeleton says, but I think recompression can be worth the file size reduction. The output from ffmpegX is pretty decent. Definitely worth trying. Dropping file size by half is worth being able to see all of my Simpsons instantly!

If you have the time and inclination, the 3ivx encoder is definitely the way to go. I just compared the video from 3ivx and ffmpegX and 3ivx matches the original MPEG1 much better. I will have to see if I can automate some of this stuff with scripts.

BTW, Quicktime's MPEG4 codec is not very good, IMHO. The video quality is bad unless you crank up the bit rate. I found 3ivx and ffmpegX to be superior at lower bit rates.

[vmpaul]

Would cleaner do the conversion any better? Not having to worry about the audio would be a big plus.