Audio issues in DNx Transcode

[Jason Diamond]

Been doing some transcodes to DNx from the proxies and realized that RED handles the audio at 32bit. AVID can only handle 24bit max thus the issue.

I have a workaround for extracting and importing audio separately but just wanted to make it known for people who had not realized or come across this issue. it's a huge pain in the ass if you spent all night transcoding especially :)

[MichaelP]

32 bit?!?!?!? Why?? Is that a setting on the camera?

Avid does 16bit and 24bit.

Thanks for the heads up Jason.

Michael

[Bruce Allen]

No, it has always been advertised as 24 bit, right? Never 32bit...

Bruce Allen
www.boacinema.com

[Jason Diamond]

well we did compressor transcodes to DNx and didnt touch the audio setting because we figured like you that it would be 24 or 16bit. but when i batch imported the transcodes after metacheater ALE i got import errors on audio and after some troubleshooting saw the files were 32bit (Big Endian). now there is the possibility that Compressor threw that little ditty in there and will suss that out after NAB but just wanted to throw it out so if you got the same error it would make a quicker troubleshoot.
plus it allowed to figure out how to workflow the following:

export audio to 24bit aiff from the QT
strip off the audio track and save(no recompression)
batch import QT in bin
batch import offline only items again after video is in and if you link to the aiff files it will shoehorn the audio into the clip as if it were the orig audio so no syncing needed.

incredible and so pleased to have found that.
plus i had called AVID tech to find out if there was a way and they said NO :'(
so i was double stoked to have figured it out!

[MichaelP]

Apparently the camera packs the 24bit into 32. Avid expects 24 as 24. This is being looked into.

Michael

[Jason Diamond]

yeah i def knew they were using the extra 8bits as pad...ian bloom surmised it was a programming issue to make it easier from a numbers standpoint but it was something neither of us had thought of or experienced. glad its being sussed out. i mean it would be one thing if it actually recorded 32bit audio but it should be 24 standard.

thanks for the update MP...see you in the desert

[Dylan Reeve]

I'm going to see if there's a way to use FFMpeg to pull the audio out of the proxies and make it usable in Avid - should be possible.

Anyone got a link to fairly small R3D with audio? Nothing we've shot has audio.

[Dylan Reeve]

ffmpeg -i A001_C013_901227_M.mov -vn -acodec pcm_s24le -ar 48000 -ac 2 testaudio.wav

This in theory should work. However FFMPEG has problems with the Camera-created file links from the reference to the R3D file...

[mov,mp4,m4a,3gp,3g2,mj2 @ 008D9308]stream 0, error opening file /ata10/1/A001_C013_901227.RDC/A001_C013_901227_001.R3D: No such file or directory
[mov,mp4,m4a,3gp,3g2,mj2 @ 008D9308]stream 1, error opening file /ata10/1/A001_C013_901227.RDC/A001_C013_901227_001.R3D: No such file or directory

The quicktime player doesn't have this problem at all. It does find the file reference (I assume it looks for the same file in the current directory if the absolute file path fails).

With FFMpeg installed on the same machine as REDline, where you can create new reference media with correct file paths, should do what's expected.

[Kevin Halverson]

Been doing some transcodes to DNx from the proxies and realized that RED handles the audio at 32bit. AVID can only handle 24bit max thus the issue.

No it doesn't. The .r3d files contain 24 bit audio data.

[Dylan Reeve]

No it doesn't. The .r3d files contain 24 bit audio data.

Apparently 24bit of data in a 32bit package with 8bits of zero padding. Or that was the report here.