On Sep 22, 2006, at 10:36 PM, Sandeep Chandna wrote:
Hi!
- Does QT allow upsampling of SampleSize (PCM 16bit input to 32 bit/
64 bit output) and Mono to Stereo/5.1 etc ? or just the downsampling ?
These questions belong on the QuickTime api mailing list. (cc'ing
the appropriate list).
I assume you're talking about the SCAudio compression API's. The
answer is yes. You can up convert to wider sample sizes. You can
also upsample the sample rate.
SCAudio does not currently allow up converting channel layouts (since
this would just result in empty channels), except the case of mono ->
stereo.
You may down convert to channel layouts with fewer numbers of
channels (e.g. 5.1 -> quad), or the same number of channels (e.g. 5.1
L,R,C,LFE,Ls,Rs -> C,L,R,Ls,Rs,LFE). It also allows you to get your
n input channels out as discrete (no mix) channels, or you can pass
the input channel layout through to the output (say, if you're just
performing a sample rate conversion on an odd channel layout, such as
L,R,C, it will let you get L,R,C out as passthru).
- Like in SoundMgr's SoundConverterGetInfo function which returned
the handle to a CompressionInfo structure, can we get this Handle
in the new API as well? or do we have to just use ASBD to do the
needful .
Look through the set of supported properties. You can use ASBD,
AudioChannelLayout, MagicCookie, CodecSpecificSettings (codec
properties in a parseable CFArray), or you can get a blob of settings
using the SCGetSettingsAsAtomContainer call.
-Brad Ford
QuickTime Engineering
Thanks
Sandeep
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