在播放iOS时从HLS流(视频)中提取/录制音频

Question

我正在使用AVPlayer播放HLS流.而且我还需要在用户按下记录按钮时记录这些流.我使用的方法是分别录制音频和视频,然后在最后合并这些文件以制作最终视频.并且它对远程mp4文件很成功.

但是现在对于HLS(.m3u8)文件,我能够使用AVAssetWriter录制视频,但是录音有问题.

我正在使用MTAudioProccessingTap处理原始音频数据并将其写入文件.我跟着这篇文章.我能够录制远程mp4音频,但它无法使用HLS流.最初我无法使用AVAssetTrack*audioTrack = [asset tracksWithMediaType:AVMediaTypeAudio] [0]从流中提取音轨.

但我能够使用KVO提取audioTracks来初始化MTAudioProcessingTap.

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
AVPlayer *player = (AVPlayer*) object;

if (player.status == AVPlayerStatusReadyToPlay)
{
    NSLog(@"Ready to play");
    self.previousAudioTrackID = 0;


        __weak typeof (self) weakself = self;

        timeObserverForTrack = [player addPeriodicTimeObserverForInterval:CMTimeMakeWithSeconds(1, 100) queue:nil usingBlock:^(CMTime time)
                {

                    @try {

                            for(AVPlayerItemTrack* track in [weakself.avPlayer.currentItem tracks]) {
                                if([track.assetTrack.mediaType isEqualToString:AVMediaTypeAudio])
                                    weakself.currentAudioPlayerItemTrack = track;

                            }

                            AVAssetTrack* audioAssetTrack = weakself.currentAudioPlayerItemTrack.assetTrack;


                            weakself.currentAudioTrackID = audioAssetTrack.trackID;

                            if(weakself.previousAudioTrackID != weakself.currentAudioTrackID) {

                                NSLog(@":::::::::::::::::::::::::: Audio track changed : %d",weakself.currentAudioTrackID);
                                weakself.previousAudioTrackID = weakself.currentAudioTrackID;
                                weakself.audioTrack = audioAssetTrack;
                                /// Use this audio track to initialize MTAudioProcessingTap
                            }
                        }
                        @catch (NSException *exception) {
                            NSLog(@"Exception Trap ::::: Audio tracks not found!");
                        }

                }];


    }
}  

我还跟踪trackID以检查曲目是否已更改.

这是我初始化MTAudioProcessingTap的方法.

-(void)beginRecordingAudioFromTrack:(AVAssetTrack *)audioTrack{
// Configure an MTAudioProcessingTap to handle things.
MTAudioProcessingTapRef tap;
MTAudioProcessingTapCallbacks callbacks;
callbacks.version = kMTAudioProcessingTapCallbacksVersion_0;
callbacks.clientInfo = (__bridge void *)(self);
callbacks.init = init;
callbacks.prepare = prepare;
callbacks.process = process;
callbacks.unprepare = unprepare;
callbacks.finalize = finalize;

OSStatus err = MTAudioProcessingTapCreate(
    kCFAllocatorDefault, 
    &callbacks, 
    kMTAudioProcessingTapCreationFlag_PostEffects, 
    &tap
);

if(err) {
    NSLog(@"Unable to create the Audio Processing Tap %d", (int)err);
    NSError *error = [NSError errorWithDomain:NSOSStatusErrorDomain
                                         code:err
                                     userInfo:nil];
    NSLog(@"Error: %@", [error description]);;
    return;
}

// Create an AudioMix and assign it to our currently playing "item", which
// is just the stream itself.


AVMutableAudioMix *audioMix = [AVMutableAudioMix audioMix];
AVMutableAudioMixInputParameters *inputParams = [AVMutableAudioMixInputParameters
    audioMixInputParametersWithTrack:audioTrack];

inputParams.audioTapProcessor = tap;
audioMix.inputParameters = @[inputParams];
_audioPlayer.currentItem.audioMix = audioMix;
}

但现在有了这个音频轨道MTAudioProcessingTap回调"准备"和"进程"永远不会被调用.

我是通过KVO获得audioTrack的问题吗？

现在我真的很感激,如果有人可以帮助我.或者可以告诉我是否使用写入方法来记录HLS流？

Answer 1

我找到了解决方案,并在我的应用程序中使用它.想早点发布,但没有时间.

因此,要使用HLS,您应该知道它们究竟是什么.为此,请在Apple网站上查看. HLS Apple

以下是我要遵循的步骤.1.首先获取m3u8并解析它.您可以使用这个有用的套件M3U8Kit解析它.使用此工具包,您可以获得M3U8MediaPlaylist或M3U8MasterPlaylist(如果它是主播放列表)如果您获得主播放列表,您也可以解析它以获得M3U8MediaPlaylist

(void) parseM3u8
{
NSString *plainString = [self.url m3u8PlanString];
BOOL isMasterPlaylist = [plainString isMasterPlaylist];


NSError *error;
NSURL *baseURL;

if(isMasterPlaylist)
{

    M3U8MasterPlaylist *masterList = [[M3U8MasterPlaylist alloc] initWithContentOfURL:self.url error:&error];
    self.masterPlaylist = masterList;

    M3U8ExtXStreamInfList *xStreamInfList = masterList.xStreamList;
    M3U8ExtXStreamInf *StreamInfo = [xStreamInfList extXStreamInfAtIndex:0];

    NSString *URI = StreamInfo.URI;
    NSRange range = [URI rangeOfString:@"dailymotion.com"];
    NSString *baseURLString = [URI substringToIndex:(range.location+range.length)];
    baseURL = [NSURL URLWithString:baseURLString];

    plainString = [[NSURL URLWithString:URI] m3u8PlanString];
}



M3U8MediaPlaylist *mediaPlaylist = [[M3U8MediaPlaylist alloc] initWithContent:plainString baseURL:baseURL];
self.mediaPlaylist = mediaPlaylist;

M3U8SegmentInfoList *segmentInfoList = mediaPlaylist.segmentList;

NSMutableArray *segmentUrls = [[NSMutableArray alloc] init];

for (int i = 0; i < segmentInfoList.count; i++)
{
    M3U8SegmentInfo *segmentInfo = [segmentInfoList segmentInfoAtIndex:i];

    NSString *segmentURI = segmentInfo.URI;
    NSURL *mediaURL = [baseURL URLByAppendingPathComponent:segmentURI];

    [segmentUrls addObject:mediaURL];
    if(!self.segmentDuration)
        self.segmentDuration = segmentInfo.duration;
}

self.segmentFilesURLs = segmentUrls;



}

您可以看到,您将从m3u8获取指向.ts文件的链接.

2. 现在将所有.ts文件下载到本地文件夹中.
3. 将这些.ts文件合并到一个mp4文件和导出.你可以使用这个美妙的C库TS2MP4来做到这一点

然后你可以删除.ts文件或在需要时保留它们.