Max possible audio quality for DVDSP?

[Geoffrey Cox]

Hi,

Mastering a DVD at the moment and have run into the problem of DVDSP 'bitrate too high' warning. Some research suggested it's the audio which I want to burn at 24bit 48K (i.e. max spec for DVD) so I removed the audio and it burnt fine so this is clearly the issue. I still want the best audio I can get so does anyone know any way round this or the best audio compression I can get away with (I compress everything in Compressor first)?

Thanks,

Geoff

[Jonathan Jones]

Hopefully this will help:

From wikipedia-

"The official allowed formats for the audio tracks on a DVD Video are:
--PCM: 48 kHz or 96 kHz sampling rate, 16 bit or 24 bit Linear PCM, 2 to 6 channels, up to 6144 kbit/s. N.B. 16-bit 48 kHz 8 channel PCM is allowed by the DVD-Video specification but is not well-supported by authoring applications or players.

--AC-3: 48 kHz sampling rate, 1 to 5.1 (6) channels, up to 448 kbit/s

--DTS: 48 kHz or 96 kHz sampling rate, 2 to 6.1 channels, Half Rate (768 kbit/s) or Full Rate (1536 kbit/s)

--MP2: 48 kHz sampling rate, 1 to 7.1 channels, up to 912 kbit/s

DVDs can contain more than one channel of audio to go together with the video content, supporting a maximum of 8 simultaneous audio tracks per video. This is most commonly used for different audio formats—DTS 5.1, AC-3 2.0 etc.—as well as for commentary and audio tracks in different languages."



-Jon

[Geoffrey Cox]

Cheers Jonathan. Did some calculations and if I stick with 2 channels of audio at 48K 24bit looks like the maximum bit rate for the video is about 7.2kb/s - I had it set at 8.2 (though the average was at 6.9) so maybe that's the problem. Good old Wikipedia - didn't realise that to calculate the bit rate of PCM audio you simply multiply the sampling rate x bit depth x no. of channels. So for stereo at 48K, 24 bit it's 2304 kb/s. I then used an online DVD bitrate calculator to get the 7.2 max bitrate.

Will try it tomorrow!

Geoff

[Jonathan Jones]

Originally Posted by Geoffrey Cox

Will try it tomorrow!

Geoff

Please report back as to the results. I'm curious as to the outcome.

Cheers,

-Jon

[Geoffrey Cox]

Jonathan,

It worked - set the max bit rate in Compressor to 7.2 which meant the highest average bit rate allowed was 6.1. Seemed a bit low but the video looks fine on my relatively modest HDTV. Another bitrate calculator suggested 7.4 would be OK but I played it safe. I might try using 16bit audio as this would allow about 8.2 as the max bitrate, to see if I can see any difference in the video resolution.

Obviously all this depends on the length of the video - mine as about 40 minutes.

Next problem is how to get menu text to look anything like acceptable in DVDSP!!

Geoff

[Jonathan Jones]

Very glad to hear it worked. That's good news.

Thanks much for the update.

-Jon