Looking for suggestions: DD+ -> AC3 / DTS conversion

[NanoBot]

Hi everybody,

during the last days I did backups from my first HD-DVDs ( Matrix trilogy europe/germany ) into matroska files. During this process I learned that the DD+ variant used on HD-DVDs do not contain a "normal" ac3 core, whereas the variant used on BD does. My amplifier is connected through a digital coaxial cable to my pc and is only able to decode ac3 or dts. At the same time I wanted to be able to playback the backups without the need of additional commercial software like PowerDVD; instead I wanted to playback them using only mpc_hc and the MS VC1 runtimes. Therefore I needed to convert the DD+ streams either to ac3 or dts, which worked fine using eac3to.

Nevertheless I would like to read your suggestions concerning the adequate target format and bitrate for such an audio track conversion. The HD-DVDs are containing DD+ tracks with 640kBit/s, and DD+ is said to be a more efficient compression than ac3 was. That leads me to the question if there is a rule of thumb which bitrate, either in ac3 or in dts is qualitywise equivalent to a DD+ track at 640kBit/s ?

C.U. NanoBot

[Snowknight26]

Actually, I don't believe Blu-ray's E-AC3 streams contain AC3 cores.

Anyway, go for full bitrate AC3 or DTS, 640kbps or 1536kbps respectively.
Check here (http://forum.doom9.org/showthread.php?p=1175483#post1175483), here (http://forum.doom9.org/showthread.php?p=1175562#post1175562), and here (http://forum.doom9.org/showthread.php?p=1176144#post1176144) for more info.

[Blue_MiSfit]

DD+ isn't much better than DD.

It's a little better at low bitrates (doesn't brutally low-pass filter at 256 and 384kbps like DD does), but its main "features" are increased channel and bitrate support (to fill up those giant optical discs the studios want to sell us ;))

DD+ -> DD at 448-640kbps is my personal recommendation. DTS is wasteful at 1.5mbps, IMHO.

448kbps will maintain full frequency response, but you get a bit less compression at 640.. I can't tell much difference between source DD+ tracks, and 384kbps DD transcodes (and I do a lot of these)

~MiSfit

[madshi]

Actually, I don't believe Blu-ray's E-AC3 streams contain AC3 cores.
They do.

[NanoBot]

Hi,

thanks for your opinions. My first intuition was to convert the audio tracks to ac3 640kBit/s, and I think I will continue using this target format.

C.U. NanoBot

[Snowknight26]

They do.

If thats the case, why do E-AC3 streams have to be converted to AC3 when trying to extract the AC3 'core' using tools such as eac3to?

[madshi]

If thats the case, why do E-AC3 streams have to be converted to AC3 when trying to extract the AC3 'core' using tools such as eac3to?
Because only Blu-Ray E-AC3 streams have an AC3 core while HD DVD E-AC3 stream have not. And the only Blu-Ray E-AC3 streams in the world are those from the Dolby demo disc. There is not a single Blu-Ray movie disc which uses E-AC3.

[Snowknight26]

Because only Blu-Ray E-AC3 streams have an AC3 core while HD DVD E-AC3 stream have not. And the only Blu-Ray E-AC3 streams in the world are those from the Dolby demo disc. There is not a single Blu-Ray movie disc which uses E-AC3.

I'm looking at the eac3to output of my Transformers disc and it clearly shows E-AC3.

[madshi]

I'm looking at the eac3to output of my Transformers disc and it clearly shows E-AC3.
Transformers Blu-Ray? That would be the first Blu-Ray with an E-AC3 track then! Is it the new original Transformers Blu-Ray or is it a transcode done by some user?

Edit: According to hidefdigest the original new Transformers Blu-ray has TrueHD and AC3 tracks. E-AC3 tracks are not listed in the specs. Ok, hidefdigest is not always reliable, of course...

[sehgal.v7]

@Madshi
Transformers on Blu Ray (UK) contains DTS 5.1 1509Kbps 16-bit as Primary track & DD AC3 5.1 640Kbps / DD AC3 2.0 224Kbps as Secondary Tracks.
Only HD-DVD of Transformers contains E-AC3(DD+).

[nautilus7]

Transformers Blu-ray has TrueHD and AC3 audio.

@sehgal.v7

UK blu-ray? I believe this is a custom made blu-ray from HD DVD. Can you pm me the link where you found it?

[sehgal.v7]

Bene's unofficial Blu Ray Specifications Thread
hxxp://forum.blu-ray.com/showthread.php?t=3338

[nautilus7]

I didn't manage to find it there... Anyway, this doesn't prove anything.

[sehgal.v7]

@nautilus7
"Anyway, this doesn't prove anything." ??

[nautilus7]

Yeah, I mean, that even if it is in that list, it doesn't necessarily mean that the specs are correct. I find it hard to believe that the UK BD (if exists) has only plain DTS and AC3 audio.

Better stop here, cause we 're out of topic.

[madshi]

I believe that movie in that list is "The Transformers" and not "Transformers"... ;)

http://www.imdb.com/title/tt0092106/

[sehgal.v7]

oopz.. sowwie thn :-)!!

[Snowknight26]

Just dumped the disc:
eac3to v2.58
command line: eac3to.exe "G:\Backups\Transformers" 1)
------------------------------------------------------------------------------
M2TS, 2 video tracks, 5 audio tracks, 8 subtitle tracks, 2:23:27
1: Chapters, 24 chapters
2: h264/AVC, 1080p24 /1.001 (16:9)
3: h264/AVC, 480p24 /1.001 (20:11)
4: TrueHD/AC3, English, 5.1 channels, 48khz, dialnorm: -27dB
5: AC3, French, 5.1 channels, 640kbps, 48khz, dialnorm: -27dB
6: AC3, Spanish, 5.1 channels, 640kbps, 48khz, dialnorm: -27dB
7: AC3, English, 2.0 channels, 192kbps, 48khz, dialnorm: -27dB
8: E-AC3, English, 2.0 channels, 192kbps, 48khz, dialnorm: -27dB
9: Subtitle (PGS), English
10: Subtitle (PGS), English
11: Subtitle (PGS), French
12: Subtitle (PGS), Spanish
13: Subtitle (PGS), Portuguese
14: Subtitle (PGS), French
15: Subtitle (PGS), Spanish
16: Subtitle (PGS), English

[madshi]

Just dumped the disc:
Can I have a small sample (50MB)? I don't understand how this can work. I think eac3to doesn't even handle Blu-Ray style E-AC3 tracks correctly yet. So how can it properly detect this? Maybe it's an HD DVD style DD+ track? Wouldn't make much sense to me, though.

[Snowknight26]

http://www.stfcc.org/misc/transformers.sample.m2ts

[madshi]

http://www.stfcc.org/misc/transformers.sample.m2ts
Thank you! This one really has E-AC3 as a secondary (commentary) audio track - with *no* AC3 core. It seems that the AC3 core + E-AC3 extension logic is used on Blu-Ray only for main tracks, but not for secondary threads. I was not aware of that. So here's how it seems to be:

E-AC3 usage on Blu-Ray/HD DVD:
(1) HD DVD: E-AC3 frames only, no AC3 core.
(2) Blu-Ray main tracks: AC3 core + E-AC3 extension frames.
(3) Blu-Ray secondary tracks: E-AC3 frames only, no AC3 core.

eac3to currently supports (1) and (3), but the more complicated (2) is not supported yet. But (2) is not used on any Blu-Ray disc except one Dolby demo disc, AFAIK. And Transformers is the first Blu-Ray where I've seen (3). Fortunately (3) is identical in format to (1), so it's automatically supported by eac3to.