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Half-Bitrate DTS - odd numbers

Posted: Mon Nov 04, 2013 2:00 pm
by neilwilkes
If I use a 768Kbps DTS file, it seems to think it is twice the length it is in reality.
Form is padded (.dts) as DLP seems to struggle with Compact (.cpt) form.

Is there a workaround?

Re: Half-Bitrate DTS - odd numbers

Posted: Thu Nov 07, 2013 1:05 pm
by Vapymid
Does it affect the compiled project or does it only show the wrong duration in the Assets bin?

Regards

Re: Half-Bitrate DTS - odd numbers

Posted: Fri Nov 08, 2013 5:22 am
by neilwilkes
No Idea.
I will check

Re: Half-Bitrate DTS - odd numbers

Posted: Tue Mar 18, 2014 2:53 am
by videonut
neilwilkes wrote:If I use a 768Kbps DTS file, it seems to think it is twice the length it is in reality.
Form is padded (.dts) as DLP seems to struggle with Compact (.cpt) form.
This sounds like simple math.
384 is max for DVD audio as I know it. 768 is exactly double that, hence illegal, so you get double the length to compensate.

Re: Half-Bitrate DTS - odd numbers

Posted: Tue Mar 18, 2014 4:33 am
by neilwilkes
videonut wrote:
neilwilkes wrote:If I use a 768Kbps DTS file, it seems to think it is twice the length it is in reality.
Form is padded (.dts) as DLP seems to struggle with Compact (.cpt) form.
This sounds like simple math.
384 is max for DVD audio as I know it. 768 is exactly double that, hence illegal, so you get double the length to compensate.
Say what?
384 is max for DVD audio what, exactly?
For starters, I assume you mean "audio on DVD-Video" in the interests of precision as DVD-Audio is a totally different format.
Audio in DVD-Video is as follows:
Mandatory - LPCM, AC3 - LPCM to 16/48 resolution (1536kbps) with support for 20 & 24-bit and 96KHz sample rates being optional, but if used players must be capable of SRC on the fly, although a 16-bit player will truncate the larger word lengths. AC3 is mandatory up to 448kbps in 5.1, although the channel count is not mandatory as 5.1 so it is within specs to use 448kbps stereo.
DTS was always optionally supported in either full or half bitrate (1536kbps or 768kbps) - both types are spec legal.

Re: Half-Bitrate DTS - odd numbers

Posted: Mon Mar 24, 2014 9:24 pm
by videonut
Say what?
384 is max for DVD audio what, exactly? For starters, I assume you mean "audio on DVD-Video" ...
Thanks for that clarification. Yes, audio on DVD video. I've been under the impression that 384kbps was the max for over 10 years. I use ac3 exclusively, but have never had a need to actually encode the audio that high.

It all stems from a paper I read back then (circa 2004) which had the name of the Phillips Corp. on it. It listed several audio scenarios for DVD video, and In all of them the 'main' (for want of a better word) audio was listed as 384k, with 2 or 3 other audio streams in each scenario shown at lower bitrates - 64 or possibly 128. It's hard to remember that far back. I don't recall any particular format being listed. I think the document was already several years old before I saw it. Anyway, I took that to mean 384 was the upper limit. Mea culpa, mea culpa.

Re: Half-Bitrate DTS - odd numbers

Posted: Tue Aug 25, 2020 9:02 am
by neilwilkes
videonut wrote:
Mon Mar 24, 2014 9:24 pm
Say what?
384 is max for DVD audio what, exactly? For starters, I assume you mean "audio on DVD-Video" ...
Thanks for that clarification. Yes, audio on DVD video. I've been under the impression that 384kbps was the max for over 10 years. I use ac3 exclusively, but have never had a need to actually encode the audio that high.

It all stems from a paper I read back then (circa 2004) which had the name of the Phillips Corp. on it. It listed several audio scenarios for DVD video, and In all of them the 'main' (for want of a better word) audio was listed as 384k, with 2 or 3 other audio streams in each scenario shown at lower bitrates - 64 or possibly 128. It's hard to remember that far back. I don't recall any particular format being listed. I think the document was already several years old before I saw it. Anyway, I took that to mean 384 was the upper limit. Mea culpa, mea culpa.
With sincere apologies for dredging up an ancient thread, but I failed to notice this reply back in the day and on reading this today I thought that it may still be relevant for some folks if I explained bitrates & what is/is not DVD legal a bit better.

Let's start with AC3.
In stereo mode, AC3 is usually at 192kbps, but this can be higher if required - as much as 448kbps is DVD legal for an AC3 (Dolby Digital) file, regardless of channel count. 5.1 should always be at 448kbps even though this is not full range and cuts off at either 16 or 18kHz (I cannot remember which off the top of my head) and to get full 20Hz-20kHz range a bitrate of 640kbps is required, which is not DVD legal and if used may or may not play properly. In all honesty I have only ever seen this bitrate for AC3 on certain Pink Floyd discs, which is plain daft as a DTS stream could have been used instead.

Now for DTS.
There are 2 different bitrates permitted using 2 different extension types - .cpt (or 'compact') and .dts (or 'padded'). We have Apple to blame for this, nobody else, as the Apple tool for DVD only used to accept compact type for some reason best known to Steve Jobs. The bitrates are either full (1536kbps, the same as 16/48 LPCM) or half (768kbps) - both are acceptable, although half bitrate is a more aggressive data reduction.

LPCM.
LPCM audio can be 16, 20 or 24-bit at 48 or 96kHz. The caveat with high resolution in DVD-Video is that the bitrate for 24/96 PCM stereo is 4,608kbps (almost 5Mbps) - almost half of the available biit budget for the title, with it's absolute maximum of 10.08Mbps so adding high quality video to this ain't gonna happen but a slideshow is perfectly okay as long as your authoring tool allows slideshows to have their chapter marks assignable from a button (Scenarist SD does not actually allow this for some reason whereas DLP certainly does and also has it's wonderful 'Audio Title' option, which really helps)

Bit Depths and Sample Rates.
For AC3 and DTS both, it is far far better to feed your encoder with 24-bit audio if the encoder will accept it (the good ones do) and it decodes to proper 24-bit as well when done this way. DTS also allows 2 sample rates - 48kHz and 96kHz, both will use the same data rate of 1536kbps.
It is not legal to use 96kHz for AC3.

I hope this is useful to someone.