Hi, I'm trying to decode a HLS livestream with VideoToolbox. The CMSampleBuffer is successfully created (OSStatus == noErr). When I enqueue the CMSampleBuffer to a AVSampleBufferDisplayLayer the view isn't displaying anything and the status of the AVSampleBufferDisplayLayer is 1 (rendering). When I use a VTDecompressionSession to convert the CMSampleBuffer to a CVPixelBuffer the VTDecompressionOutputCallback returns a -8969 (bad data error). What do I need to fix in my code? Do I incorrectly parse the data from the segment for the CMSampleBuffer? let segmentData = try await downloadSegment(from: segment.url) let (sps, pps, idr) = try parseH264FromTSSegment(tsData: segmentData) if self.formatDescription == nil { self.formatDescription = try CMFormatDescription(h264ParameterSets: [sps, pps]) } if let sampleBuffer = try createSampleBuffer(from: idr, segment: segment) { try self.decodeSampleBuffer(sampleBuffer) } func parseH264FromTSSegment(tsData: Data) throws -> (sps: Data, pps: Data, idr: Data) { let tsSize = 188 var pesData = Data() for i in stride(from: 0, to: tsData.count, by: tsSize) { let tsPacket = tsData.subdata(in: i..<min(i + tsSize, tsData.count)) guard let payload = extractPayloadFromTSPacket(tsPacket) else { continue } pesData.append(payload) } let nalUnits = parseNalUnits(from: pesData) var sps: Data? var pps: Data? var idr: Data? for nalUnit in nalUnits { guard let firstByte = nalUnit.first else { continue } let nalType = firstByte & 0x1F switch nalType { case 7: // SPS sps = nalUnit case 8: // PPS pps = nalUnit case 5: // IDR idr = nalUnit default: break } if sps != nil, pps != nil, idr != nil { break } } guard let validSPS = sps, let validPPS = pps, let validIDR = idr else { throw NSError() } return (validSPS, validPPS, validIDR) } func extractPayloadFromTSPacket(_ tsPacket: Data) -> Data? { let syncByte: UInt8 = 0x47 guard tsPacket.count == 188, tsPacket[0] == syncByte else { return nil } let payloadStart = (tsPacket[1] & 0x40) != 0 let adaptationFieldControl = (tsPacket[3] & 0x30) >> 4 var payloadOffset = 4 if adaptationFieldControl == 2 || adaptationFieldControl == 3 { let adaptationFieldLength = Int(tsPacket[4]) payloadOffset += 1 + adaptationFieldLength } guard adaptationFieldControl == 1 || adaptationFieldControl == 3 else { return nil } let payload = tsPacket.subdata(in: payloadOffset..<tsPacket.count) return payloadStart ? payload : nil } func parseNalUnits(from h264Data: Data) -> [Data] { let startCode = Data([0x00, 0x00, 0x00, 0x01]) var nalUnits: [Data] = [] var searchRange = h264Data.startIndex..<h264Data.endIndex while let range = h264Data.range(of: startCode, options: [], in: searchRange) { let nextStart = h264Data.range(of: startCode, options: [], in: range.upperBound..<h264Data.endIndex)?.lowerBound ?? h264Data.endIndex let nalUnit = h264Data.subdata(in: range.upperBound..<nextStart) nalUnits.append(nalUnit) searchRange = nextStart..<h264Data.endIndex } return nalUnits } private func createSampleBuffer(from data: Data, segment: HLSSegment) throws -> CMSampleBuffer? { var blockBuffer: CMBlockBuffer? let alignedData = UnsafeMutableRawPointer.allocate(byteCount: data.count, alignment: MemoryLayout<UInt8>.alignment) data.copyBytes(to: alignedData.assumingMemoryBound(to: UInt8.self), count: data.count) let blockStatus = CMBlockBufferCreateWithMemoryBlock( allocator: kCFAllocatorDefault, memoryBlock: alignedData, blockLength: data.count, blockAllocator: nil, customBlockSource: nil, offsetToData: 0, dataLength: data.count, flags: 0, blockBufferOut: &blockBuffer ) guard blockStatus == kCMBlockBufferNoErr, let validBlockBuffer = blockBuffer else { alignedData.deallocate() throw NSError() } var sampleBuffer: CMSampleBuffer? var timing = [calculateTiming(for: segment)] var sampleSizes = [data.count] let sampleStatus = CMSampleBufferCreate( allocator: kCFAllocatorDefault, dataBuffer: validBlockBuffer, dataReady: true, makeDataReadyCallback: nil, refcon: nil, formatDescription: formatDescription, sampleCount: 1, sampleTimingEntryCount: 1, sampleTimingArray: &timing, sampleSizeEntryCount: sampleSizes.count, sampleSizeArray: &sampleSizes, sampleBufferOut: &sampleBuffer ) guard sampleStatus == noErr else { alignedData.deallocate() throw NSError() } return sampleBuffer } private func decodeSampleBuffer(_ sampleBuffer: CMSampleBuffer) throws { guard let formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer) else { throw NSError() } if decompressionSession == nil { try setupDecompressionSession(formatDescription: formatDescription) } guard let session = decompressionSession else { throw NSError() } let flags: VTDecodeFrameFlags = [._EnableAsynchronousDecompression, ._EnableTemporalProcessing] var flagOut = VTDecodeInfoFlags() let status = VTDecompressionSessionDecodeFrame( session, sampleBuffer: sampleBuffer, flags: flags, frameRefcon: nil, infoFlagsOut: nil) if status != noErr { throw NSError() } } private func setupDecompressionSession(formatDescription: CMFormatDescription) throws { self.formatDescription = formatDescription if let session = decompressionSession { VTDecompressionSessionInvalidate(session) self.decompressionSession = nil } var decompressionSession: VTDecompressionSession? var callback = VTDecompressionOutputCallbackRecord( decompressionOutputCallback: decompressionOutputCallback, decompressionOutputRefCon: Unmanaged.passUnretained(self).toOpaque()) let status = VTDecompressionSessionCreate( allocator: kCFAllocatorDefault, formatDescription: formatDescription, decoderSpecification: nil, imageBufferAttributes: nil, outputCallback: &callback, decompressionSessionOut: &decompressionSession ) if status != noErr { throw NSError() } self.decompressionSession = decompressionSession } let decompressionOutputCallback: VTDecompressionOutputCallback = { ( decompressionOutputRefCon, sourceFrameRefCon, status, infoFlags, imageBuffer, presentationTimeStamp, presentationDuration ) in guard status == noErr else { print("Callback: \(status)") return } if let imageBuffer = imageBuffer { } }