Optical Tracks and Dolby

[Onti]

Gone with the wind - Optical Mono



The wizard of Oz - Optical Mono (dual)



Star Wars - Dolby Stereo (along with Dolby Digital between the holes)



“Gone with the wind” and “The wizard of Oz” are from the year 1939, but has different optical tracks. Dolby Laboratories introduced Dolby A in 1965, that “The wizard of Oz” print uses Dolby?

[deleted user]

Looks like Dolby A started being used 1974: https://en.wikipedia.org/wiki/Dolby_Stereo

Those old dual mono tracks don't use Dolby A afaik. From what I understand, Dolby A went hand-in-hand with Dolby Stereo, so any Dolby Stereo film after 1974 should also use Dolby A.

[pipefan413]

Looks like Dolby A started being used 1974: https://en.wikipedia.org/wiki/Dolby_Stereo

Those old dual mono tracks don't use Dolby A afaik. From what I understand, Dolby A went hand-in-hand with Dolby Stereo, so any Dolby Stereo film after 1974 should also use Dolby A.

Bingo. I wrote a big ol' summary of a lot of this stuff elsewhere, maybe I should repost it here for those interested...

EDIT: Done, though I posted the bulk of this quite a long time ago and haven't checked it again recently. If any of those who know more about this stuff than me want to step in to "well actually" me, please do! I'm posting it to try to help clear some of this stuff up for newcomers interested in the topic, so any clarifications may help and I certainly don't want to accidentally misinform. Anyway, here it is, in it's >3,500-word glory! https://fanrestore.com/thread-3467.html


The bit that pertains to the above statement about Dolby A in the context of Dolby Stereo and mono soundtracks is as follows:

Dolby A noise reduction was used for film production purposes starting with A CLOCKWORK ORANGE (1971), but it wasn’t implemented for the audio that was actually printed onto the theatrical film prints until it was used on the optical mono track of prints of CALLAN (1974). The trouble was, since the Dolby process involved applying the aforementioned pre-emphasis to the optical track, cinemas therefore had to install new audio decoders to de-emphasise these tracks back to sound how they were intended to sound. Not every cinema could necessarily afford to do this, and since stereophonic sound was also starting to rise to prominence around the same time, cinema owners didn’t want to spend a bunch of money on Dolby A decoders that could still only do mono anyway. This is one of the main reasons that there were still a large number of cinemas with somewhat antiquated monophonic audio systems when STAR WARS was released in 1977.

That being the case, Dolby came up with a solution to introduce their noise reduction process to an implementation of optical stereophonic film sound that was more cost-effective than the magnetic 6-track surround sound used on formats like Todd-AO and could occupy the limited space available on a 35 mm print by using only 2 tracks instead of 6. The Dolby noise reduction process helped with the dynamic range issue caused by the limited physical space available for the 2 optical tracks, since the pre- and de-emphasis increased the dynamic range during playback, but the problem of there being no centre channel had to be dealt with as well.

[Onti]

I’m a newcomer in sound and I don’t fully understand all the concepts but I’ll try to explain better my concerns and to do so I’ll divide the question into 2 parts.

Part 1.

Is this an original 1939 release print or a newer print?:



I mean, optical mono and optical mono (dual, with the same information on both channels) tracks coexist in 1939? If so, why? Why (in 1939) some prints have 2 channels and others only 1 being both mono? That’s my main doubt.

Part 2.

If we scan a print like this:



How to properly preserve the audio? ¿DTS-HD Master Audio 1.0 o LPCM 1.0?

If we scan a print like this:



How to properly preserve the audio? ¿DTS-HD Master Audio 2.0 (mono) o LPCM 2.0 (mono)?

If we scan a print like this:



How to properly preserve the audio? ¿DTS-HD Master Audio 2.0 (estereo) o LPCM 2.0 (estereo)?

It is essential for me to understand this to decide which films need an audio preservation and which don't. As I understand, LPCM can cause problems with some players.

https://www.hometheaterforum.com/communi...ys.318900/

[Chewtobacca]

How to properly preserve the audio? ¿DTS-HD Master Audio 2.0 (mono) o LPCM 2.0 (mono)?

How to properly preserve the audio? ¿DTS-HD Master Audio 1.0 o LPCM 1.0?

Both DTS-HD MA will preserve the audio properly. They are lossless codecs. For 2.0 and 1.0, I don't bother with DTS-HD MA though.

The thread to which you linked is talking only about 1.0 LPCM, and only with certain amplifiers. It's a non-issue, in my view, but you can always convert 1.0 to 2.0, if you prefer, by duplicating the channel: L and R will be the same. Both 1.0 and 2.0 are acceptable ways to present mono audio, found on commercial discs.

How to properly preserve the audio? ¿DTS-HD Master Audio 2.0 (estereo) o LPCM 2.0 (estereo)?

It doesn't matter.

[Onti]

Thanks a lot, Chewtobacca.