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-   -   Newbie question about the SD302 (https://www.dvinfo.net/forum/all-things-audio/105016-newbie-question-about-sd302.html)

Ty Ford January 8th, 2009 10:38 AM

Quote:

Originally Posted by Petri Kaipiainen (Post 756237)
Here we have to note also that the specks for XH-A1 in the quote above are vastly INFERIOR to the DV audio given for HV20. DV audio 16/48 is totally uncomressed WAV type audio, HDV MP2 audio at 384 kbs is about five fold compressed compared to DV audio and unsuitable for critical work. This is unfortunate, but necessary to save space to be able to fit the HDV data to a DV-tape.

Just to get facts staight.

Yes. And I had a heck of a time trying to tell a HV30 shooter recently that the reason he was not happy with his "HD" footage was due to the fact that it was really HDV, and very compressed.

Regards,

Ty Ford

Daniel Epstein January 8th, 2009 01:52 PM

Quote:

Originally Posted by Petri Kaipiainen (Post 756237)
Here we have to note also that the specks for XH-A1 in the quote above are vastly INFERIOR to the DV audio given for HV20. DV audio 16/48 is totally uncomressed WAV type audio, HDV MP2 audio at 384 kbs is about five fold compressed compared to DV audio and unsuitable for critical work. This is unfortunate, but necessary to save space to be able to fit the HDV data to a DV-tape.

Just to get facts staight.

The way I understand the difference between DV and HDV audio is like this
The HDV audio is inferior to the DV audio on the same camera (like the XHA1) because the audio signal is compressed into and with the Video stream into the GOP while the DV audio is recorded seperately from the video stream onto the tape. Not sure if they could have chosen less compression for the audio and still fit it in the stream although I would have thought so. There apparently was space on the tape for simultaneous DV quality audio recording with the HDV Video but it was always out of sync by something close to the length of the GOP so no manufacturer seemed to want to deal with it.

Ty Ford January 8th, 2009 02:17 PM

Dan,

Yes, I had surmised that the mpeg audio was probably due to the latency problems; video encoding taking longer than PCM audio. So they needed to slow down the audio so it would sync with the video.

Regards,

Ty Ford

Daniel Epstein January 8th, 2009 07:29 PM

Ty,
Yes that was what I was told about the Mpeg audio as well but they still had room on the tape for the out of sync PCM signal to be recorded which could have been dealt with in post. A little tricky perhaps but might have been worth it. For example I am not sure if anyone would be able to access the PCM audio on firewire at the same time as the Mpeg. Might have taken more than a little engineering. HDV was an unusual advancement over DV in that a higher quality video image over the previous spec was married to a lower quality audio signal from the previous spec when it probably didn't have to be the only option due to physical constraints of data rate recording limitations.
Certainly not much we can do about it now but it is good to know that newer is not always better quality in all respects or better designed.


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