Blu-ray Ripping - Most Quality

[LionGod8]

Hello everyone.

I make low bitrate (4,000-6,000 kbps) 1080p Blu-ray rips
and need your opinion about audio encoding - how to keep most quality.

In short:
When I rip a Blu-ray and want to encode the audio:
1. In case of only DTS audio track on Blu-ray - what is better, to encode to 640 kbps CBR AC3 or to VBR with another encoder (like AAC or Vorbis or maybe something else) ?
2. In case Blu-ray has one lossless DTS track and one 640 kbps AC3 track - what's better, to keep the 640 kbps CBR AC3 track as is or to encode to VBR (with another encoder) from the DTS lossless track ?
3. Is there a way of keeping all 7.1 channels when encoding to AC3 ?

Thanks in advance.

[Blue_MiSfit]

1) If you're really worried about giving your video all the bits you can, I'd suggest going with AAC at something like 256kbps for 5.1 channel.

2) Good question. Probably re-encoding the lossless source to AAC, but do your own experiments. Nobody can tell you which method is better.

3) Nope

[LionGod8]

1) Actually I want to keep a good quality audio track, so I want the bitrate to go someting like 640 kbps. BUT as I know that AC3 isn't so efficient relative to "modern" encoders (like AAC or Vorbis) especially because it encodes only in CBR mode (which supposed to inferior to VBR), then I decided to encode with some other VBR encoder.
But then I hear almost everyone around me (who also make rips of blu-ray) - that they keep a (or encode to) AC3 audio track in their movie file.
So I ask myself: "Does AC3 have some advantage that other encoders don't have?", "Maybe it is actually more efficient than say AAC or Vorbis...?"

4) By the way, while trying to decide which encoder is preferable between AAC and Vorbis, I noticed that AAC couldn't encode 6.1 channels (only 5.1 or 7.1). Is that correct?

10x!

[Blue_MiSfit]

AC3 is much LESS efficient than AAC or similar. However, it has the advantage of being directly compatible with S/PDIF. So, if you're sending the audio to a receiver, and you don't want to use HDMI for your audio (in my case), or don't want to decode to analog, AC3 can just travel on the S/PDIF interface. All other formats (except DTS but it's lolBIG) need to be transcoded to AC3 on the fly for S/PDIF playback. That is - assuming you want 5.1. If you're okay with stereo, then uncompressed PCM fits just fine on S/PDIF.

AC3 needs 384kbps for 5.1 channel to sound reasonably good. At that bitrate, AAC eats its lunch.

If you can afford 640kbps, just stick with AC3. If you need to go lower, but care about S/PDIF, you could maybe do AC3 as low as 384kbps. If you need to go lower than 384kbps, or don't care about S/PDIF, then go AAC.

I'd draw a flow chart, but it's pretty damned simple :)

[LionGod8]

OK, I got it. So I'll stick with the AC3 @ 640 kbps.
But what do I do with 6.1 and 7.1 channels, if I want to keep all channels?

[Blue_MiSfit]

Keep them in their original formats, probably. I don't know if any commonly used AAC encoders support 7.1 channels, I've never tried. I do know that standard AC3 doesn't support more than 5.1.

[LionGod8]

Yes, AAC does support 7.1 (Nero AAC Encoder) and Vorbis too.
But, I want to be consistent with my rips, and if I go with AC3 then I need to stick with it (in all of my encodes).
So, is there any way to keep 7.1 channels or should I go with AAC (or Vorbis) on all my rips?

10x!

[LionGod8]

Is there any way of encoding to Dolby Digital Plus (E-AC3) in order to keep more than 5.1 channels?

[Anacletus]

Is there any way of encoding to Dolby Digital Plus (E-AC3) in order to keep more than 5.1 channels?

I don't think without buying commercial (and expensive) software. But i might be wrong :p

[Blue_MiSfit]

I believe there is rudimentary E-AC3 encoding in ffmpeg / libav now - or at least there was a patch floating around I think. In any case, I doubt this supports any of the improvements in E-AC3.

[Mole]

If the audio is 5.1, I recommend you stick to AC3.

Currently many software and hardware implementations has problems sending the 5.1 audio properly for AAC and without correct configuration, in most cases it will only send stereo signal instead.

So it depends on the purpose of your rips. If you're using personally yourself, then there's no need to worry about this problem if your setup manage to send 5.1 audio from AAC or OGG properly.

But if you want 100% problem free compatibility, just use AC3 and nobody will have problems playing the 5.1 audio.

Bitrate of 448 should be plenty though and I doubt there is really much difference between 448 and 640.

If the BD has Dolby True HD, then I would simply use the AC3 640 core of it, so there's no re-encoding involved.
Remember that the AC3 track has been professionally mixed and compressed, which is likely going to be better than what you'd get by re-encoding the DTS tracks yourself. I also believe the dynamic range of AC3 and DTS may be different, so a re-encoding may not produce an optimum result.

If it's only has DTS-HD Master, then you can re-encode it to AC3. But make sure that you are able to re-encode the DTS-HD audio and not just the DTS-core.

For example, you'll need eac3to + ArcSoft or Sonic decoders.
http://forum.doom9.org/showthread.php?t=125966