以下是针对iOS 8的Swift进行压缩的代码,它可以令人惊奇地压缩,从35 mb下降到2.1 mb.

func convertVideo(inputUrl: NSURL,outputURL: NSURL) 
   {
    //setup video writer
    var videoAsset = AVURLAsset(URL: inputUrl,options: nil) as AVAsset

    var videoTrack = videoAsset.tracksWithMediaType(AVMediaTypeVideo)[0] as AVAssetTrack

    var videoSize = videoTrack.naturalSize

    var videoWriterCompressionSettings = Dictionary(dictionaryLiteral:(AVVideoAverageBitRateKey,NSNumber(integer:960000)))

    var videoWriterSettings = Dictionary(dictionaryLiteral:(AVVideoCodecKey,AVVideoCodecH264),(AVVideoCompressionPropertiesKey,videoWriterCompressionSettings),(AVVideoWidthKey,videoSize.width),(AVVideoHeightKey,videoSize.height))

    var videoWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo,outputSettings: videoWriterSettings)

    videoWriterInput.expectsMediaDataInRealTime = true

    videoWriterInput.transform = videoTrack.preferredTransform


    var videoWriter = AVAssetWriter(URL: outputURL,fileType: AVFileTypeQuickTimeMovie,error: nil)

    videoWriter.addInput(videoWriterInput)

    var videoReaderSettings: [String:AnyObject] = [kCVPixelBufferPixelFormatTypeKey:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange]

    var videoReaderOutput = AVAssetReaderTrackOutput(track: videoTrack,outputSettings: videoReaderSettings)

    var videoReader = AVAssetReader(asset: videoAsset,error: nil)

    videoReader.addOutput(videoReaderOutput)



    //setup audio writer
    var audioWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeAudio,outputSettings: nil)

    audioWriterInput.expectsMediaDataInRealTime = false

    videoWriter.addInput(audioWriterInput)


    //setup audio reader

    var audioTrack = videoAsset.tracksWithMediaType(AVMediaTypeAudio)[0] as AVAssetTrack

    var audioReaderOutput = AVAssetReaderTrackOutput(track: audioTrack,outputSettings: nil) as AVAssetReaderOutput

    var audioReader = AVAssetReader(asset: videoAsset,error: nil)


    audioReader.addOutput(audioReaderOutput)

    videoWriter.startWriting()


    //start writing from video reader
    videoReader.startReading()

    videoWriter.startSessionAtSourceTime(kCMTimeZero)

    //dispatch_queue_t processingQueue = dispatch_queue_create("processingQueue",nil)

    var queue = dispatch_queue_create("processingQueue",nil)

    videoWriterInput.requestMediaDataWhenReadyOnQueue(queue,usingBlock: { () -> Void in
        println("Export starting")

        while videoWriterInput.readyForMoreMediaData
        {
            var sampleBuffer:CMSampleBufferRef!

            sampleBuffer = videoReaderOutput.copyNextSampleBuffer()

            if (videoReader.status == AVAssetReaderStatus.Reading && sampleBuffer != nil)
            {
                videoWriterInput.appendSampleBuffer(sampleBuffer)

            }

            else
            {
                videoWriterInput.markAsFinished()

                if videoReader.status == AVAssetReaderStatus.Completed
                {
                    if audioReader.status == AVAssetReaderStatus.Reading || audioReader.status == AVAssetReaderStatus.Completed
                    {

                    }
                    else {


                        audioReader.startReading()

                        videoWriter.startSessionAtSourceTime(kCMTimeZero)

                        var queue2 = dispatch_queue_create("processingQueue2",nil)


                        audioWriterInput.requestMediaDataWhenReadyOnQueue(queue2,usingBlock: { () -> Void in

                            while audioWriterInput.readyForMoreMediaData
                            {
                                var sampleBuffer:CMSampleBufferRef!

                                sampleBuffer = audioReaderOutput.copyNextSampleBuffer()

                                println(sampleBuffer == nil)

                                if (audioReader.status == AVAssetReaderStatus.Reading && sampleBuffer != nil)
                                {
                                    audioWriterInput.appendSampleBuffer(sampleBuffer)

                                }

                                else
                                {
                                    audioWriterInput.markAsFinished()

                                    if (audioReader.status == AVAssetReaderStatus.Completed)
                                    {

                                        videoWriter.finishWritingWithCompletionHandler({ () -> Void in

                                            println("Finished writing video asset.")

                                            self.videoUrl = outputURL

                                                var data = NSData(contentsOfURL: outputURL)!

                                                 println("Byte Size After Compression: \(data.length / 1048576) mb")

                                                println(videoAsset.playable)

                                                //Networking().uploadVideo(data,fileName: "Test2")

                                            self.dismissViewControllerAnimated(true,completion: nil)

                                        })
                                        break
                                    }
                                }
                            }
                        })
                        break
                    }
                }
            }// Second if

        }//first while

    })// first block
   // return
}

这是我的UIImagePickerController调用compress方法的代码

func imagePickerController(picker: UIImagePickerController,didFinishPickingMediaWithInfo info: [NSObject : AnyObject])
{
    // Extract the media type from selection

    let type = info[UIImagePickerControllerMediaType] as String

    if (type == kUTTypeMovie)
    {

        self.videoUrl = info[UIImagePickerControllerMediaURL] as? NSURL

        var uploadUrl = NSURL.fileURLWithPath(NSTemporaryDirectory().stringByAppendingPathComponent("captured").stringByAppendingString(".mov"))

        var data = NSData(contentsOfURL: self.videoUrl!)!

        println("Size Before Compression: \(data.length / 1048576) mb")


        self.convertVideo(self.videoUrl!,outputURL: uploadUrl!)

        // Get the video from the info and set it appropriately.

        /*self.dismissViewControllerAnimated(true,completion: { () -> Void in


        //self.next.enabled = true

        })*/
    }
}

正如我上面提到的,这个文件大小减少了,但是当我得到文件(它仍然是.mov类型)时,quicktime无法播放. Quicktime最初尝试转换它,但中途失败(打开文件后1-2秒)我甚至测试了AVPlayerController中的视频文件,但它没有提供有关电影的任何信息,它只是一个播放按钮没有蚂蚁加载,没有任何长度只是“ – ”的时间通常在播放器. IE是一个不会播放的损坏的文件.

我确定它与写入资产的设置有关,因为它是视频写作或音频写作我根本不知道.甚至可能是读取导致其破坏的资产.我已经尝试更改变量,并设置不同的键读取和写入,但我没有找到正确的组合,这可以吸收,我可以压缩,但得到一个损坏的文件.我不确定,任何帮助将不胜感激. Pleeeeeeeeease.