Filming in surround sound and capture properties.

[evmiller]

My Digital Camera is a Sony DCR-HC90 with the optional 4ch surround sound microphone. The camera is set to 16-bit stereo with the mic off, but when the surround mic is plugged into the camera, it automatically switches from 16 bit stereo to 12-bit 4ch. surround. My question is this, I've been recording with the surround sound mic on the camera, but I've been capturing the video using DV type-1 and the clip propeties are showing they are being captured in 12-bit stereo. Is my audio being down-sampled from 4 audio streams down to two? Some guy I know told me I had to capture in DV type-2 to preserve the surround from the camera. I've been using type-1 to avoid syc problems. Have I been using the right properties.

[DVDDoug]

I think I read somewhere that the DV spec allows two 12-bit, or two 16-bit channels, or four 12-bit channels. I'll see if I can find that reference again...

Found it! From Wikipedia:

AUDIO

DV allows either 2 digital audio channels (usually stereo) at 16 bit resolution and 48 kHz sampling rate, or 4 digital audio channels at 12 bit resolution and 32 kHz sampling rate. For professional or broadcast applications, 48 kHz is used almost exclusively. In addition, the DV spec includes the ability to record audio at 44.1 kHz (the same sampling rate used for CD audio), although in practice this option is rarely used. DVCAM and DVCPRO both use locked audio while standard DV does not. This means that at any one point on a DV tape the audio may be +/- 1/3 frame out of sync with the video. This is the maximum drift of the audio/video sync though it is not compounded throughout the recording. In DVCAM and DVCPRO recordings the audio sync is permanently linked to the video sync.

It works-out to the same audio-bitrate for both formats. 2x16x48 = 1,536kbps and 4x12x32 = 1,536kbps. So, it takes the same amount of space on the tape/disk to store 4 channels.