Re: Convert AudioBufferList to CMSampleBuffer
Re: Convert AudioBufferList to CMSampleBuffer
- Subject: Re: Convert AudioBufferList to CMSampleBuffer
- From: Jimgreen <email@hidden>
- Date: Wed, 09 May 2012 09:19:53 -0400
Jimgreen8
On May 9, 2012, at 7:01, patrick machielse <email@hidden> wrote:
> Op 9 mei 2012, om 08:51 heeft Heinrich Fink het volgende geschreven:
>
>>> CMSampleTimingInfo timing = { CMTimeMakeWithSeconds(1 / 44100.0, 1), kCMTimeZero, kCMTimeInvalid };
>>
>> This might not be doing what you expect. CMTimeMakeWithSeconds(1 / 44100.0, 1) will actually be rounded off to [value=0, timescale=1], meaning your sample timing info will contain a duration of zero, which I am sure is not what you aimed for. Use CMTimeMake(1, 44100) instead.
>
> Thank you Heinrich,
>
> It seems that CMTimeMakeWithSeconds(1 / 44100.0, 1) was indeed the problem. CMTimeMake(1, 44100) makes my export code work!
>
>> I recommend you to look over the header documentation in CMSampleBuffer.h about CMSampleBufferCreate, especially the section "Example of usage for uncompressed non-interleaved audio:”. This really is the best source of documentation regarding CoreMedia.
>
> Yes, I used that information to create the code I have so far. But because it's only 'pseudo code' translating it into a working example required some trial and error (and friendly help from outside...).
>
> '-12731': kCMSampleBufferError_RequiredParameterMissing would not have indicated a problem with CMTimeMakeWithSeconds to me. It's better than the infamous '-50' error -- but not much better.
>
> Thanks again,
>
> patrick
>
>
>> On May 8, 2012, at 22:40 , patrick machielse wrote:
>>
>>> On iOS I need to write data coming in from an AUGraph/Unit to file. To this end I need to convert sample data contained in an AudioBufferList to a CMSampleBuffer in order to append it to a AVAssetWriterInput.
>>>
>>> It seems there isn't a lot of info available on how to do that exactly (and successfully). I've managed to come up with the following code, which uses an available ASBD struct:
>>>
>>> - (void)recordData:(AudioBufferList *)data frames:(UInt32)numberOfFrames
>>> {
>>> CMSampleBufferRef buff = NULL;
>>> CMFormatDescriptionRef format = NULL;
>>> OSStatus error = CMAudioFormatDescriptionCreate(kCFAllocatorDefault, &asbd, 0, NULL, 0, NULL, NULL, &format);
>>>
>>> CMSampleTimingInfo timing = { CMTimeMakeWithSeconds(1 / 44100.0, 1), kCMTimeZero, kCMTimeInvalid };
>>> error = CMSampleBufferCreate(kCFAllocatorDefault, NULL, false, NULL, NULL, format, numberOfFrames, 1, &timing, 0, NULL, &buff);
>>>
>>> error = CMSampleBufferSetDataBufferFromAudioBufferList(buff, kCFAllocatorDefault, kCFAllocatorDefault, 0, data);
>>> if ( error ) { NSLog(@"CMSampleBufferSetDataBufferFromAudioBufferList returned error: %ld", error); }
>>>
>>>
>>> In the last line the error is '-12731': kCMSampleBufferError_RequiredParameterMissing. I'm not sure which that should be, there are so many?
>>>
>>> Has anyone solved this before?
>
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