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Author Topic: Analog sound question Charles Greenlee Jedi Master Film Handler Posts: 801 From: Savannah, Ga, U.S. Registered: Jun 2006 posted 06-25-2006 12:22 AM                        Ok, I know I'm asking to compare apples to oranges. That said. If you had to quantify the current quality of the on film analog sound in terms of bitrate, what would you consider it closest to? I know that analog doesn't actually have a bitrate, but it does have fidelity, and many other aspects, I'm just looking for an overall comparison. I'm figuring maybe 128k on a good system, with clean heads and clean film. And the main limiting factor on analog's quality would be the inherent nose produced by the media, right?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 06-25-2006 12:30 AM                     Odd answer...read the rules quickly and fix this post before we close it and boot your account.  |  IP: Logged Charles Greenlee Jedi Master Film Handler Posts: 801 From: Savannah, Ga, U.S. Registered: Jun 2006 posted 06-25-2006 12:51 AM                        Umm, ok. I'm guessing it was the topic. I read the rules to begin with, but I guess the topic was too cryptic, fixed that.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 06-25-2006 05:04 AM                     quote: Charles Greenlee And the main limiting factor on analog's quality ...is the dynamic range in itself - which would peak out at 50 to 60dB.on a good day..whereas digital can push the envelope over 100dB without trying.. Like the analog recordings of vinyl, open reel, and cassette (we won't touch 8tracks..they didn't even come close..) having the same, basic dynamic output range within these above factors.. One can take an analog source and convert it to a 128k bitrate Mp3, but the sound would slightly suffer due to the 'lossy format" that the Mp3 format uses during the conversion from WAV to the Mp3. A good analog soundtrack when read and reproduced correctly, if you want to compare such, can sound as good (or even better) as a 320k plus variable bitrate Mp3. For using the constant bitrate isn't the real good way to compress since so much info is lost in keeping the filesize at a budget level and try to keep quality intact at the same time. Yes, definitely an Apple to Oranges comparision - analog against digital..how you slice and eat the fruit.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 06-25-2006 09:42 AM                        A few rules, first? Assume 2 track, Dolby SR optical. Probably 70 db effective s/n and 20-16000 Hz. (Dolby tracks are filtered above that and you can't project much above that in a medium cinema-sized room) Louis  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 06-25-2006 11:02 AM                     Hmmm sticky question! But in mine opinion, I think is closest to 192kbps mp3, considering You have SR and well system!  |  IP: Logged Charles Greenlee Jedi Master Film Handler Posts: 801 From: Savannah, Ga, U.S. Registered: Jun 2006 posted 06-25-2006 11:59 AM                        Yes, I was considering 2channel Dolby SR. I was throwing around a few ideas in my head, and was looking at a current mono print. Stereo has 2 tracks that take up that small space. Mono, has one track, that is twice the size as a single track from the stereo. So it should, in theory, be able to have a better dynamic range, and a lower media noise level. A mono analog print, that is 2nd gen., meaning the soundtrack is straight from the master, and not copy of a copy of a copy, could actually have a higher quality than a digital recording? But just on a single track. That is if you had decent analog sound equipment, of course. True we were comparing apples and oranges, but were relating their quality, which they both have, just doing it using digital terms. Thx guys, I got something to play around with.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 06-25-2006 03:45 PM                     The apple/orange thing is a big deal here. If you have a reasoanbly perfect Dolby SR soundtrack, you won't be able to hear any defects. Even if you a 192kbps MP3 stream, you'll be able to hear compression artifacts (well, it depends on your ear). Trying to equate compression artifacts to SNR isn't so straightforward. --jhawk  |  IP: Logged Charles Greenlee Jedi Master Film Handler Posts: 801 From: Savannah, Ga, U.S. Registered: Jun 2006 posted 06-25-2006 06:36 PM                        Well, I don't buy the 192kbps so much because of lack of clairty in the analog, and lack of dynamic range. Mainyl what I was looking for is a comparitive benchmark on quality. Like DTS would be about 256k, etc. I have CD's, which are 160k, that come out clearer and w/ negligable artifacting, than the onboard analog in just about every theatre I've worked at. Of course part of that could be poor tone adustment, or equalization, at playback. Too much low end will make it sound murky, etc. I'm just goofing off with some sound stuff, and wasy trying to figure out where the breaking point is on the optical track, what can be adjusted to make it keep up if not suprass the current digital formats. The mono format, being double sized compared to a stereo track, seems like I'm barking up the right tree. Only problem is it's just 1 channel. A remarkably clear channel, but only 1. It's more just for kicks than anything, but I am learning from it.  |  IP: Logged Patrick de Groot Expert Film Handler Posts: 161 From: Sprang-Capelle, Netherlands Registered: Apr 2001 posted 06-30-2006 07:04 AM                     Your question doesn't make much sense cause Dolby Digital is compressed audio (just like mp3). With compressed audio the following things are important for the resulting perceived quality: -audio source is uncompressed audio with a high sample rate -high enough resulting compressed bitrate -used compressing algorithm (codec) mp3, aac, ogg, ... The bitstream of a normal audio cd is 1411.2 kbps (kilo-bit-per-second) which is uncompressed audio (16 bit 44,1 KHz)(16 * 44100 * 2). Compression artefacts sound a lot different than analog recording/playback "problems". A better question would be what equivalent an analog soundtrack has in terms of digital recording quality (sample rate, resolution).  |  IP: Logged Robert Minichino Master Film Handler Posts: 350 From: Haskell, NJ, USA Registered: Dec 2005 posted 06-30-2006 07:43 AM                        You're talking about a compressed bitrate, which isn't comparable as stated above because of different codecs, etc., which all throw away different parts of the original signal (hopefully ones we can't hear ). But you can compare an analog source to an uncompressed digital audio bitrate. For the sampling rate, multiply the analog -10dB point by 2.2 (Nyquist frequency is 2x, but you need some room for the transition band), so that gets you about a 35kHz sampling rate for a 16kHz -10dB point. For 70dB dynamic range, we can see how many bits gives us a quantization noise floor -70dB or more down from 0dBFS. 12 bits gives us a 72dB dynamic range (log2(10**(70.0/20)) = 11.6 bits, so round up to 12, 20*log10(2**12) = 72dB). So, stereo means we've got a pair of 12 bit samples occurring at 35kHz, so 2*12*35 = 840 kbit/sec, compared to CD at 1,400 kbit/sec as stated above.  |  IP: Logged Charles Greenlee Jedi Master Film Handler Posts: 801 From: Savannah, Ga, U.S. Registered: Jun 2006 posted 06-30-2006 09:11 PM                        I a round about way, then optical, in it's current form, even with a new print, clean heads and good processor, is no where near CD quality, relatively speaking. CD quality should be no where near digital cinema formats quality, that is unless the compression used by the digital formats degrades the signal below CD quality, which I wouldn't think it would. Thanks for the formulae. I can use it. So I'll go write it down in my noteboock when I get to it tomorrow. Left it at work. Ok, on to my other questions. What is the relative quality then of Dolby Digital, DTS, and SDDS? I've been expiramenting with the only optical cell I could scrounge before they scrapped our old white light readers. I found out that I can emulate a mono cell by ganging the two indiviual cells, up together. This seemed to have a greater dynamic range. Though this was done in the lab at school, with an led powered by a function generator, And with the cell hooked to our o-scope. Unfortunatly, I don't have a real soundhead I can experiment with, yet.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 07-01-2006 10:31 AM                        Charles; there is even a difference in what analog can do. For example, an expert alignment of a red reader through a decent preamp can get you 16,000 hz flat. Very few soundheads are adjusted to or remain in that condition. To the extent that you fail this "maximum" you degrade the analogue. Same goes for level, crosstalk, etc. The fact that mono is more robust is correct. Without Dolby, stereo would have been too noisy to tolerate. Hence it had to wait until suitable NR was available. 2 channel analogue optical was experimented in the 40's, but was too noisy. Now we are comparing apples, oranges, pears & bannanas! Louis  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 07-01-2006 11:36 AM                     Louis, experimental two-channel optical stereo goes back further than that; at least to the mid '30s, when the Alan Blumlein recordings were made. web page I don't know if anybody else made any before this. Some of these recordings still exist, I heard the amateur dramatic one mentioned on the web page a few years ago. The quality wasn't great by modern standards, but I wouldn't say it was much worse than contempory mono tracks. Basically the same system was revived in the '50s, and got nowhere. There were many 'high-quality' sound systms over the years: Fantasound, Warnerphonic, Perspecta, Cinerama, Cinemascope, Todd-AO etc. All of these were either short-lived, or little-used. Most films were released in mono optical, and even where there was a stereo release, most cinemas ran them in mono. These systems were expensive of course, but they were available, if the demand had been there for them. Both Dolby 'A' type NR, and the Sansui QS matrix encoder/decoder were available several years before Bolby stereo film tracks were introduced. Even when they were introduced, the conversion didn't happen overnight; it took many yearsfor cinemas to convert to stereo, there are still a few mono only equipped ones today. I think the delay in conversion to stereo film sound was more economic and market led than technological.  |  IP: Logged Charles Greenlee Jedi Master Film Handler Posts: 801 From: Savannah, Ga, U.S. Registered: Jun 2006 posted 07-02-2006 02:35 AM                        I just came up with an idea on how to use the existing sountrack real estate, to allow for another descrete channel, at full mono fidelity and response. Damn, now I just need the resources to test it out. It's a solid idea but I don't want to broadcast it so it can't be jumped, but I need some more resources. Grrr.  |  IP: Logged

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