AudioConverter Problems
AudioConverter Problems
- Subject: AudioConverter Problems
- From: Herbie Robinson <email@hidden>
- Date: Mon, 1 Aug 2005 03:31:52 -0400
I've been using the AudioConverter (10.3.9 with Quick Time 7) and I
have it running for a few file types, but I'm having trouble with
It's working fine on PCM and MP3, but I am having trouble with
FormatID 0x76647661 (kAudioFormatVariableDurationDVAudio).
Quicktime kQTSoundDescriptionPropertyID_AudioStreamBasicDescription
gives me an ASBD with the sample rate at 48K, format id 0x76647661,
bytes per packet of 120K, channels per frame 2 and everything else
zeroed.
Quicktime delivers a progression of 120K packets containing 1600 or
1602 samples totaling 8008 samples every 5th buffer; so, that seems
to be doing the right thing (aside from the ugliness of having to
read the entire video frame to get the audio...).
The catch is that every time I ask for 8008 samples from the
AudioConverter, it asks Quicktime for 15 packets, not 5. After a
very short period of time, the AudioConverter gives up and returns
kAudioConverterErr_InvalidInputSize -- Not surprising, considering it
is putting more stuff into its buffer than it is taking out!
I've gone to a good bit of trouble to always call
AudioConverterFillComplexBuffer with a number of samples that is the
SCM with the frame rate to make sure I don't hit any bugs where the
audio converter has to hang onto things between calls and that didn't
help.
kQTSoundDescriptionPropertyID_MagicCookie didn't return a magic
cookie for this conversion, but probably doesn't need to.
Questions:
Is this supposed to work in 10.3.9?
10.4.1?
Is kQTSoundDescriptionPropertyID_MagicCookie the right thing to use
to get a magic cookie for the AudioConverter? The reason i ask is
that QT does return a magic cookie for PCM, but the AudioConverter
doesn't accept it?
Also, a minor problem I noticed is that
kAudioConverterPropertyCalculateOutputBufferSize
returns no noErr status and a size of zero for a common PCM streams.
I got this both using Quicktime I/O and AudioFileReadPackets.
The avoidance it pretty trivial, just treat a size of zero as a if
one got an error code, but I suspect this isn't intentional.
--
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** http://www.curbside-recording.com/ **
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