? bits for HD

dvideo2 wrote on 5/27/2009, 4:51 PM
I see the spec (48,000hz) for HD audio everywhere I look, but I can't
seem to pinpoint the bit rate. Can 16 bit audio with 48,000hz be considered HD audio or does it have to jump up in bit rate(24 or 32)?
Thanks, I looked, but can't find the answer to this.

Also, if I'm using 16 bit audio on an HD timeline in vegas 8 and eventualy want to export as HD, what will the result be?

Thanks again

Comments

pwppch wrote on 5/27/2009, 5:22 PM
bit rate and bit depth are two different things.

Bit Rate is really data rate or data transfer rate.

Bit depth controls the dynamic range of sampled audio. The more bits you sample at the larger the dymanic range.

In Vegas when you are editing you are working at a specific bit depth. This PCM audio. This is what your audio hardware supports and is by default 16 bits of resolution. The bit rate of PCM audio is determined by the sample rate and the bit depth.

When you render you can control the bit rate depending on the format you are rending to. The codec you use to encode your audio determines and controls this. They can have a wide variety of bit rates.

I believe the standard for HDV is stereo (2-channel) at 384 kbit/s (192 kbit/s per channel); with an option for 4 channels at 96 kbit/s per channel as an option.

Peter
jbolley wrote on 5/28/2009, 11:57 AM
Interesting question! Thanks for the info Peter.
So:
DV is 48KHz 16 bit PCM uncompressed audio
HDV is 48KHz 192kb/s MPEG1 layer2 compressed audio

and we learn that "Hi Def" (at least in DV land) is less def for the audio.

Doing some searching I found some info re: audio on blu-ray disks - another HD delivery option:

What audio codecs will Blu-ray support?

Linear PCM (LPCM) - up to 8 channels of uncompressed audio. (mandatory)
Dolby Digital (DD) - format used for DVDs, 5.1-channel surround sound. (mandatory)
Dolby Digital Plus (DD+) - extension of Dolby Digital, 7.1-channel surround sound. (optional)
Dolby TrueHD - lossless encoding of up to 8 channels of audio. (optional)
DTS Digital Surround - format used for DVDs, 5.1-channel surround sound. (mandatory)
DTS-HD High Resolution Audio - extension of DTS, 7.1-channel surround sound. (optional)
DTS-HD Master Audio - lossless encoding of up to 8 channels of audio. (optional)

Please note that this simply means that Blu-ray players and recorders will have to support playback of these audio codecs, it will still be up to the movie studios to decide which audio codec(s) they use for their releases.

http://www.blu-ray.com/faq/#bluray_audio_codecs

Jesse
Geoff_Wood wrote on 5/28/2009, 3:37 PM
dvideo2 - you possibly need to do some background research on what is: bit depth, sample rate, and bit-rate.

They have unfortunately seem to have become a little blurred in 'popular culture' with the advent of lossy-encoding.


geoff