CCE bitrates

[Lucius Snow]

Hello,

I export DV films to MPEG 2 with 3 VBR passes. They're usually between 30 and 60 min and with a PCM - 48 kHz- 16 bit - stereo audio track (= 1536 kbit/s). For my first encoding, i put the max. value to 8400 kbit/s, the average to 8000 kbit/s and the min. at 0. Since the max. total bitrate can't be over 10 000 kbit/s for a DVD playback, i'll let the max at 8400 kbit/s. But i was wondering what would be the best values for the average and the min. to get the best quality possible. I heard the difference between the average and the max. must be more than this.

What do you think about it ? What bitrates do you advice me for 30-60 min of MPEG 2 encoding to put on a DVD ?

Thanks in advance.

[SaSi]

Variable Bitrate encoding is a tradeoff between size and quality. The encoder seeks the portions of the video that don't really need a high bitrate and allocates this to more demanding portions.

Selecting an average and max bitrate that are close, tends to cancel the effect of VBR. An extreme example would be to set them both to the same value. It would be the equivalent of CBR encoding with the time to do the multiple passes virtually wasted.

If you want to encode short video with DV source and are happy to store an hours worth of content on a DVD, you could encode at 8500CBR with a single pass and have excellent quality and high speed.

If you want to fit, say, 2 hours content, you should aim for 4800 VBR with 1+2 passes having your min bitrate set to 0 and max set to 8400. This would really be a tradeoff, since high motion scenes might suffer. Not very probable with CCE which makes an excellent job of properly allocating bitrate.

Perhaps a good tradeoff would be fitting 90 minutes on a DVD with a VBR rate of 6000kbps.

Also, consider encoding audio to AC3. It could reduce your required bitrate for audio to 1/4th or 1/5th and give you just the extra 500-600kbps you need to add to video bitrate to properly fit 90 minutes on a DVD.

[Lucius Snow]

Ok, i'll go for 8400 kbit/s in CBR for 30-60 min if then it's the same (or even better) quality results as my current settings in VBR. Indeed, it'll be a big gain of time.

About the sound, i'll stick on PCM. AC3 stereo sounds bad to my ears. Even a MP3 encoded properly in LAME and at the same bitrate is better.

Thanks for the advices.
Cheers

[Lucius Snow]

Oh .. just a last question :

I see in CCE SP that i can choose CBR in one pass and multipass. You said onepass would give excellent quality. What does multipass change in CBR ? Would be it better ? I'm looking for the best quality possible (whatever the time it takes to encode).