when are you coming out with a new LD player??
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| Any LD's and DVD's with bit-identical AC3 soundtracks? https://forum.lddb.com/viewtopic.php?f=12&t=3599 |
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| Author: | happycube [ 05 Jan 2014, 08:40 ] |
| Post subject: | Any LD's and DVD's with bit-identical AC3 soundtracks? |
I don't know when/if I'd get around to doing anything with it, but it would help in a decoding attempt to have matching binary data. Since I don't really need an AC3 decoder for my own setup (2.0pcm is fine), it'd be nice to match the data against a 'known' source. Any such matching disks out there? (Video Essentials, maybe?) |
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| Author: | Guest [ 06 Jan 2014, 09:53 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
Unfortunately not, ld is 44100 and dvd is 48000 so the header (at least) for each frame will differ. |
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| Author: | happycube [ 06 Jan 2014, 20:54 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
Regular LD PCM is 44.1khz (and is identical to CD Audio, so if someone/me writes a decoder there's plenty of reference material!), but I think AC3 LD is/can be 48K. Do you have anything confirming that only 44.1 was used on AC3? |
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| Author: | rein-o [ 06 Jan 2014, 20:56 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
when are you coming out with a new LD player?? ________________________________ the rein-o official signature:
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| Author: | elviscaprice [ 06 Jan 2014, 21:40 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
From what I can gleam from this paper on AC3 it is in 48khz. Might be some useful information here for you. http://web.archive.org/web/200612310254 ... c3spec.pdf |
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| Author: | acuozzo [ 06 Jan 2014, 21:56 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
rein-o wrote: when are you coming out with a new LD player?? Now that question is a bit off-topic for this thread, don't you agree?Remember: Threads are like cable TV channels playing crummy football games... you can easily skip over 'em! |
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| Author: | happycube [ 06 Jan 2014, 22:38 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
The on-topic version of that is "When are you coming out with a new AC3 decoder?" It's possible using affordable components (the capture card hack I already have, or upverter + RTL-SDR) but I have no idea when it'll exist.  (could use some help from the people who actually designed the encoding, as the decoding/error correction data tables aren't part of the AC3-on-LD patent. The standard AC3 spec is helpful, at least - thanks!) |
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| Author: | Guest [ 07 Jan 2014, 11:11 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
A capture from ld to pc via spdif (which uses the external clock signal) is at 44100, I get a 44100 2 ch wav file that when played from my pc via spdif to my avr is decoded as Ac3... I have been concentrating on dts so my knowledge of ac3 isn't great but both ac3 and dts captures are bit perfect as they playback flawlessly from my pc via my avr. |
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| Author: | happycube [ 07 Jan 2014, 18:40 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
AC3 on Laserdisc uses a completely different encoding system (replacing the right analog channel) - so unless you have an AC3 decoder (from the seperate/special coaxial AC3 RF port on an LD player), you're just hearing the standard digital track. DTS, OTOH, replaces the standard digital track, so a bit perfect PC capture can be decoded with software. |
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| Author: | substance [ 07 Jan 2014, 19:53 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
my a/v processor shows sampling frequency of incoming digital signal.. I can try an ac-3 disc tonight and tell you what the sampling rate is. any particular title are you interested in?. I have plenty of ac-3 discs it might be best to try out the ones we both own. as for identical ac-3 tracks, we will have to hunt down early dvd pressings with 384kbps ac-3 audio. there is really few. most of the later releases(from 1998 on) are in 488kbps. I want to say the first pressing of "twister" might be one. it was the very first dvd released in the US in march 1997. it has been reprinted multiple times so I don't know if subsequent versions have different audio(I know there is a dts version). the first pressing was the hated by some hard paper cover with plastic inners that warner used on early dvds. interview with the vampire mars attacks stargate beetlejuice basic instinct these above are some other dvd releases from 1997 with ac-3 audio also exist in LD with ac-3 audio. http://www.amazon.com/Terminator-2-Judg ... ator+2+dvd this version of terminator 2 confirmed to use the same DSS master used on this LD: Terminator 2: Judgment Day (1991) [LD68952-2DD] I cant tell for sure if they are bit perfect equal. these above titles are difficult to spot and find. Terminator 2 dvd was October 1997 release. Subsequent dvd releases used different name (extreme edition, ultimate edition etc..) and different cover so it is easier to find. The only give away for the other ones are the paper case warner used on early DvDs. hope this helps |
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| Author: | happycube [ 07 Jan 2014, 22:04 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
I might have that T2 LD, I'll check tonight. (From what I read in that A/52 pdf, there's a pretty good chance that I'll be able to use the CRC codes to verify decoding without having to compare against a reference, too )
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| Author: | Guest [ 08 Jan 2014, 09:46 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
Yes, I capture ld ac3 to pc via pioneer rfd-1 demodulator, sorry, should've mentioned that Last night I sampled a ld ac3 audio track at 44100 and then at 48000 and both played back fine via my avr....the dolby symbol lit up .... very confused,... I'll look into it more tonight if I have time. Anyway, it not really relevant to your discussion... apologies. |
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| Author: | sdraper [ 11 Jan 2014, 02:57 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
Indeed, it is only on the early era of DVD where DD 5.1 is at the LD standard rate of 384 kbp/s. Off the top of my head, this is most of the Warner snapper case early releases, the Matrix, and the SE DVD Bond films remastered in 5.1 and later era (done originally for LD). |
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| Author: | sdraper [ 24 Aug 2015, 22:49 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
Initial Paramount DVDs are 384 kbp/s and ports of their LDs so the ac3 may be identical. I have THE PHANTOM and MISSION IMPOSSIBLE and they seem the same. The latter is even non-anamorphic, and they include the 2 channel matrixed audio as well but in DD 2.0. |
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| Author: | happycube [ 25 Aug 2015, 02:52 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
Thanks for the heads up - and that'd make sense, Paramount made a lot of Lazydisc DVD's. Maybe someday I'll actually try to figure LD's AC3 error correction encoding out... |
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| Author: | little-endian [ 29 Aug 2015, 07:08 ] |
| Post subject: | Re: Any LD's and DVD's with bit-identical AC3 soundtracks? |
bubski wrote: Last night I sampled a ld ac3 audio track at 44100 and then at 48000 and both played back fine via my avr....the dolby symbol lit up .... very confused,... Actually you didn't. I made the same false conclusion at first when I delt with recording S/PDIF sources. When you record analog sources, in the best case, the sample rate setting in your recording software will determine the clock rate of your sound card's ADC. In the not so great case, it will rather determine in which rate it shall be converted from a fixed sample rate ("best" sad example are many Sound Blaster cards pushing everything through the fixed 48 kHz - sample rate). When you record via S/PDIF, however, your sound card's S/PDIF receiver has to lock into the sample rate of the source, no matter of what sample rate you set in your editor. Leaving annoying stuff like resampling or volume changes aside, the sound card will forward the samples "as is" and the editor will put that into a file. Your sample rate setting here eventually only determines the sample rate header in the resulting file, which is why your AC3 file, you mistakenly recorded at 44.1 kHz, will still work. However, when you have the 44.1 kHz header set and play that back, your AC3 file should play too slow including a lower pitch respectively. Of course, a simple adjustment of the file header would do it. Furthermore, since a lot of wrong information seems to be floating around the net including the allegedly 44056 Hz for PCM of NTSC LaserDiscs, the correct sample rates are: AC3: 48000 Hz PCM (and thus DTS as well of course): 44100 Hz |
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