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Re: Using VDSetCompression Milton Aupperle Thu Sep 06 06:17:28 2007


On 5-Sep-07, at 9:15 AM, Simon Raisin wrote:

Note that if I change kRawCodeType to k422YpCbCr8CodecType the call to VDSetCompression() succeeds.

Yes, likely because the VDIG does not support ARGB32/BGRA32, it only supports a YUV flavor(s). RGB24 is also not supported on the Mac (it's Windows Only), so you always have to work with ARGB32 or BGRA32 depending on Host's native endian. And numerous QT API calls for Compression will allow you to compress/decompress to RGB24 on a Mac, however they silently lie with no error messages and return buffers of ARGB32/BGRA32 instead. I filed this as a bug and was told that's they way Apple wants it.

But if I use the settings panel I can select the compression type "None", so I know that my vdig supports no compression.

This has nothing to do with what the VDIG delivers. In the Settings Panel that indicates what you want the Sequence Grabber to deliver when it's configured to record. So the SG will take whatever native format the VDIG delivers and then compress it (if possible) using your specified Compression Codec. The MungGrab Samples show this pretty well as your decompression sequence does that work.

If you want to know what the VDIG can actually deliver try calling VDGetCompressionTypes() and looking at the VDCompressionListHandle that gets returned. The VDCompressionListHandle contains at least one VDCompressionList structure and may contain more (hint, our DFG/ 1394-1 A/D converter supports 2 types and others may do more or less).

You want to extract each of of the VDCompressionList structure form the VDCompressionListHandle and then check the .cType field to determine what format the VDIG can deliver in and the the .formatFlags field indicates the depth it supports and the .typeName filed has the Codec Name.


Milton J. Aupperle
ASC - Aupperle Services and Contracting
Mac Software (Drivers, Components and Application) Specialist
#1005 - 815 14th Avenue. S.W.
Calgary Alberta T2R0N5
Proud Supporter of the "Party of Alberta"

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