Audio issue downconverting to SD

Tommy Schell · February 1st, 2010, 05:52 PM

Hi,

we heard about this a couple of weeks ago (I am probably the one you corresponded with),
I still don't have any clues as to why StreamClip or Compressor treats our files differently than it does the Sony files in terms of audio processing.
The only difference I can find between our audio tracks and Sony's, as I mentioned before, is that we have 24 bit audio and Sony has 16 bit audio on their SxS cards.
A good test would be to see how StreamClip reacts to a file from a Sony PDW-700 or 800, which is even closer to our files including 24 bit audio.

Tommy Schell

Billy Steinberg · February 1st, 2010, 07:16 PM

Tommy: I assume you have read my two messages in this thread. They explain the cause of the mono mixing.

MPEG streamclip, though marvelously powerful with respect to the video portion, is somewhat lacking in the audio portion, particularly when dealing with .mov files. MPEG Streamclip gives you no way to specify audio channel assign when you are recompressing/converting from a .mov file. So the two nano audio tracks are simply mixed as that, giving you a mono mix in the output.

The Sony created files have the audio channel track assignments set. Yours don't. It has nothing to do with 16 bit or 24 bit. Reread my message about opening a raw nano .mov file with Quicktime Player 7. Then open a raw nano file and a raw Sony file, and you'll see why there is no problem with the Sony file.

Billy

February 1st, 2010, 05:52 PM	#16
Tommy Schell Regular Crew Join Date: Nov 2007 Location: Colorado Springs, CO Posts: 65	Hi, we heard about this a couple of weeks ago (I am probably the one you corresponded with), I still don't have any clues as to why StreamClip or Compressor treats our files differently than it does the Sony files in terms of audio processing. The only difference I can find between our audio tracks and Sony's, as I mentioned before, is that we have 24 bit audio and Sony has 16 bit audio on their SxS cards. A good test would be to see how StreamClip reacts to a file from a Sony PDW-700 or 800, which is even closer to our files including 24 bit audio. Tommy Schell

February 1st, 2010, 07:16 PM	#17
Billy Steinberg Regular Crew Join Date: Nov 2008 Location: NYC Posts: 122	Tommy: I assume you have read my two messages in this thread. They explain the cause of the mono mixing. MPEG streamclip, though marvelously powerful with respect to the video portion, is somewhat lacking in the audio portion, particularly when dealing with .mov files. MPEG Streamclip gives you no way to specify audio channel assign when you are recompressing/converting from a .mov file. So the two nano audio tracks are simply mixed as that, giving you a mono mix in the output. The Sony created files have the audio channel track assignments set. Yours don't. It has nothing to do with 16 bit or 24 bit. Reread my message about opening a raw nano .mov file with Quicktime Player 7. Then open a raw nano file and a raw Sony file, and you'll see why there is no problem with the Sony file. Billy