ShazamKit constantly fail without an error

Question

Created Jun ’21

Replies 2

Boosts 0

Views 1.5k

Participants 3

In continuation to this question, I am now able to use ShazamKit in my app, but for every video I pass to it didFailWithSignature is always called:

 func session(_ session: SHSession,
       didNotFindMatchFor signature: SHSignature,
                 error: Error?) {
        DispatchQueue.main.async {
            print("match error: \(String(describing: error))")
        }
    }

with the following output:

match error: nil

This is happening even with videos that are just screen recorded video clips of Ed Sheeran for example, something that Shazam would easily recognized.

Any idea why that would happen? What I should investigate?

(the full code is also updated on my GitHub

Boost

Answer 1

Apple Designer OP

Apple

Jun ’21

This could be caused by the way the audio file is converted into PCM buffers. There's an example code snippet posted on this thread on how to convert AVAudioFile into AVAudioPCMBuffer.

0

Answer 2

OP

Apple

Sep ’21

Hi LGariv

Sorry for the delay in getting back to you but you do indeed have a conversion error in your project. I have updated the convertBuffer function from your project and I am now getting matches.

Firstly you had an assumption about the bytes per frame which was incorrect. I fixed this by reading from the asbd

let frameLength = AVAudioFrameCount(mBuffers.mDataByteSize / **asbd.mBytesPerFrame**)

Then you need to copy the memory to your output buffer, the full method is below. Please use this only as a starting point, it does not handle channels correctly and should only be used as a guide.

 func convertBuffer(sampleBuffer: CMSampleBuffer) -> AVAudioPCMBuffer {
 
        var asbd = CMSampleBufferGetFormatDescription(sampleBuffer)!.audioStreamBasicDescription!
 
        var audioBufferList = AudioBufferList()
 
        var blockBuffer : CMBlockBuffer?
 
 
 
        CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(
 
            sampleBuffer,
 
            bufferListSizeNeededOut: nil,
 
            bufferListOut: &audioBufferList,
 
            bufferListSize: MemoryLayout<AudioBufferList>.size,
 
            blockBufferAllocator: nil,
 
            blockBufferMemoryAllocator: nil,
 
            flags: 0,
 
            blockBufferOut: &blockBuffer
 
        )
 
 
 
        let mBuffers = audioBufferList.mBuffers
 
        let frameLength = AVAudioFrameCount(mBuffers.mDataByteSize / asbd.mBytesPerFrame)
 
        let pcmBuffer = AVAudioPCMBuffer(pcmFormat: AVAudioFormat(streamDescription: &asbd)!, frameCapacity: frameLength)!
 
        pcmBuffer.frameLength = frameLength
 
 
 
        memcpy(pcmBuffer.mutableAudioBufferList.pointee.mBuffers.mData, audioBufferList.mBuffers.mData, Int(audioBufferList.mBuffers.mDataByteSize))
 
        pcmBuffer.mutableAudioBufferList.pointee.mBuffers.mDataByteSize = audioBufferList.mBuffers.mDataByteSize
 
 
 
        return pcmBuffer
 
    }

Lastly, cool app, keep up the good work!

0

	func session(_ session: SHSession,
	didNotFindMatchFor signature: SHSignature,
	error: Error?) {
	DispatchQueue.main.async {
	print("match error: \(String(describing: error))")
	}
	}

	func convertBuffer(sampleBuffer: CMSampleBuffer) -> AVAudioPCMBuffer {

	var asbd = CMSampleBufferGetFormatDescription(sampleBuffer)!.audioStreamBasicDescription!

	var audioBufferList = AudioBufferList()

	var blockBuffer : CMBlockBuffer?



	CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(

	sampleBuffer,

	bufferListSizeNeededOut: nil,

	bufferListOut: &audioBufferList,

	bufferListSize: MemoryLayout<AudioBufferList>.size,

	blockBufferAllocator: nil,

	blockBufferMemoryAllocator: nil,

	flags: 0,

	blockBufferOut: &blockBuffer

	)



	let mBuffers = audioBufferList.mBuffers

	let frameLength = AVAudioFrameCount(mBuffers.mDataByteSize / asbd.mBytesPerFrame)

	let pcmBuffer = AVAudioPCMBuffer(pcmFormat: AVAudioFormat(streamDescription: &asbd)!, frameCapacity: frameLength)!

	pcmBuffer.frameLength = frameLength



	memcpy(pcmBuffer.mutableAudioBufferList.pointee.mBuffers.mData, audioBufferList.mBuffers.mData, Int(audioBufferList.mBuffers.mDataByteSize))

	pcmBuffer.mutableAudioBufferList.pointee.mBuffers.mDataByteSize = audioBufferList.mBuffers.mDataByteSize



	return pcmBuffer

	}