Preserving as much audio as I can for Blu-Ray

dxdy wrote on 5/24/2014, 7:32 AM
The choral director at the high school finally has a home Blu-Ray player, and I want to deliver the spring concert in the best possible fidelity. The source (from Canon XF100 -MXF) is (channels 1 and 2 have the same mediainfo output):



Audio #2

ID                                       : 4

Format                                   : PCM

Format settings, Endianness              : Little

Format_Settings_Wrapping                 : Frame (AES)

Duration                                 : 5mn 13s

Bit rate mode                            : Constant

Bit rate                                 : 768 Kbps

Channel(s)                               : 1 channel

Sampling rate                            : 48.0 KHz

Bit depth                                : 16 bits

Stream size                              : 28.7 MiB (1%)


It seems the best bit rate Vegas 12 offers is 192Kbps (in project media audio settings).

When authoring in DVDA 5.2, I can specify 448 Kbps.

So my audio bit rate path looks like this:


Camera -> Vegas ->  AC3 Pro ->  DVDA

  768  ->  192  ->    448   ->   448


My questions are:

1. How do I preserve the quality of the camera's high bit rate through Vegas and out to the disk?

2. If it can't be preserved, should everything be done at 192?

3. I have read that human ears cannot hear a quality difference above 320K.

4. Will a trained ear hear the difference (she has a good audio system at home).

After years of finessing the video side, this is my first foray into the depths of the audio side.

Thanks in advance for any advice.

Fred

edited to clarify both channels have same mediainfo data

Comments

craftech wrote on 5/24/2014, 8:20 AM
Use either 448 or use PCM depending upon the length of the concert (might not fit).

John
musicvid10 wrote on 5/24/2014, 8:33 AM
Use PCM 16/48, same as your source.
john_dennis wrote on 5/24/2014, 8:33 AM
File / Render As / WAV (Microsoft) (*.WAV) / 48,000 Hz, 16 Bit, Stereo, PCM
rraud wrote on 5/24/2014, 8:39 AM
I concur, 16/48k PCM. 2 channel .wav (stereo)
DeadRadioStar wrote on 5/24/2014, 3:26 PM
Don't worry about the bps, PCM is uncompressed and the best choice. It just so happens that 16/48 works out at a bit rate of 768Kbps ... uncompressed.
dxdy wrote on 5/24/2014, 3:36 PM
Thanks everyone. I rendered out the PCM and it is 8 times the size of the AC3. And it sounds better. Now I have to reduce the video bitrate and make some room on the disk.

Fred
riredale wrote on 5/25/2014, 9:13 PM
PCM audio is about 1500Kbps for stereo.

Also, there's very little difference between ac3 and PCM. What's nice about Vegas is that you can easily subtract the compressed signal from the original and hear the error signal.

Choral music especially easy to compress transparently.
PeterDuke wrote on 5/25/2014, 9:36 PM
Yes. 16 bits x 2 channels x 48 thousand samples per second = 1536 Kbps.
John_Cline wrote on 5/25/2014, 10:14 PM
Rather than reduce the bit rate of the video, you can encode AC3 audio out of Vegas at higher than 192kbps. Just select the "Stereo DVD" template under "Dolby Digital AC-3 Pro", then hit "Customize Template", then on the "Audio Service" tab, select a data rate, 384kbps should be plenty.

Then set "Dialog Normalization" to "-31 db" so it won't change your audio levels.

Finally, select the "Preprocessing" tab and set both "Line mode profile" and "RF mode profile" to "None."

Give this template a name and save it for later use.
Jumping Rascal wrote on 5/26/2014, 9:14 AM
In regards to question 4, yes, the trained ear definitely can tell the difference. I have prepared several church/community choir videos for the flock and those with a higher level of musicality always provide feedback such as the choir members on the left side of the church don't come out well or the some of the instruments are a bit muddy or the audio on the dvd didn't match the performance. Of course, I am limited by the source material that was provided to me by the choir but with Vegas, Audacity, and more recently with some of the new sound tools provided by V13 suite,especially iZotope, I have happier campers. I render in AC3 5.1 (for DVDA 5.2) but provide three separate audio tracks in the finished DVD (a regular one that sounds good on my home sound system, one with boosted higher mid frequencies to compensate for the hearing loss by some of the older choir members (tried out various audio software settings until they liked it), and a third that brought out the piano/instruments better for those performers. I'm still working on blu-ray versions but the DVDA's blu-ray chapter/menu limited functions are a bit aggravating. Good luck on your projects!
John_Cline wrote on 5/26/2014, 5:29 PM
"In regards to question 4, yes, the trained ear definitely can tell the difference. I have prepared several church/community choir videos for the flock and those with a higher level of musicality always provide feedback such as the choir members on the left side of the church don't come out well or the some of the instruments are a bit muddy or the audio on the dvd didn't match the performance."

What you're talking about is the quality of the original recording, not whether someone can hear the difference between AC3 encoded audio and the original uncompressed PCM audio. A higher AC3 encoding bitrates, even the golden ear types would be hard pressed to tell the difference between PCM and AC3 unless, perhaps, they could quickly switch between the two.