Re: Audio problem
Re: Audio problem
- Subject: Re: Audio problem
- From: "Sandeep Chandna" <email@hidden>
- Date: Wed, 14 Feb 2007 18:35:12 +0530
Brad, thanks for replying.
I tried 10 packets, but that didnt solve my problem. When my input is 48khz and output is 44khz everything is fine but when I use 22khz or lesser output frequency (for same input frequency), SCAudioFillBuffer is not returning me all the encoded packets. So my output audio duration is lesser than input duration and I get lip-sync issues. I noticed that by using 5 packets my output showed 2445312 samples (QTPro->Show movie props) whereas while using 10 packets I got 2428928 packets , That is QDesign dropped some 16k samples which is close to 1 second of audio.
Also, as I mentioned in my last mail, I cant use 5 packets for QDesign (which works sometimes) because SCAudioFillBuffer goes into endless loop of returning blank packets and gets stuck
I have been trying various things (different packet sizes) but with no luck.
Should not SCAudioFillBuffer return whatever is being fed to it?
My code is for both Win/MAC so I cant switch to AudioConverter API also. Please help!!
Thanks
Sandeep
On 12/02/07, Brad Ford <email@hidden> wrote:
On Feb 12, 2007, at 10:11 AM, Sandeep Chandna wrote:
> Hi,
>
> I am using SCAudioFillBuffer to encode my audio in QDesign
> format but am facing a weird issue.
>
> If I set the number of packets to 50 , SCAudioFillBuffer
> returns me lesser number of packets than expected and so I get
> blank audio in the end.
QDesign audio packets are huge. There very likely isn't 50 packets
worth of source material if you're getting less than you asked for.
>
> Whereas if I set the number of packets to 5, the behaviour
> is undefined. Sometimes encoded file has full audio, at other times
> SCAudioFillBuffer keeps returning
> blank data endlessly and I have to forcibly terminate the
> loop. I am setting the endOfStream in the mySCAudioCallBack
> properly , is SCAudioFillBuffer broken for
> QDesign ? or am I missing something ?
This is a quirky behavior of QDesign. SCAudio doesn't expose a
property to ask the minimum number of packets required by a format,
but AudioConverter does, so you could verify this behavior by
substituting your SCAudioFillBuffer stuff with
AudioConverterFillComplexBuffer on an AudioConverter instance. I
believe QDesign requires a minimum of 10 packets.
-Brad Ford
QuickTime Engineering
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