Question

我需要在不降低分辨率的情况下缩小使用混合应用拍摄的视频的尺寸，因此我尝试修改cordova video editor plugin以通过更改比特率来缩小视频的尺寸。我试图使用SDAVAssetExportSession但没有取得任何成功，并且获得了大量的CVPixel错误。插件代码是：

- (void) transcodeVideo:(CDVInvokedUrlCommand*)command
{
    NSDictionary* options = [command.arguments objectAtIndex:0];

    if ([options isKindOfClass:[NSNull class]]) {
        options = [NSDictionary dictionary];
    }

    NSString *assetPath = [options objectForKey:@"fileUri"];
    NSString *videoFileName = [options objectForKey:@"outputFileName"];

    CDVQualityType qualityType = ([options objectForKey:@"quality"]) ? [[options objectForKey:@"quality"] intValue] : LowQuality;

    NSString *presetName = Nil;

    switch(qualityType) {
        case HighQuality:
            presetName = AVAssetExportPresetHighestQuality;
            break;
        case MediumQuality:
        default:
            presetName = AVAssetExportPresetMediumQuality;
            break;
        case LowQuality:
            presetName = AVAssetExportPresetLowQuality;
    }

    CDVOutputFileType outputFileType = ([options objectForKey:@"outputFileType"]) ? [[options objectForKey:@"outputFileType"] intValue] : MPEG4;

    BOOL optimizeForNetworkUse = ([options objectForKey:@"optimizeForNetworkUse"]) ? [[options objectForKey:@"optimizeForNetworkUse"] intValue] : NO;

    float videoDuration = [[options objectForKey:@"duration"] floatValue];

    BOOL saveToPhotoAlbum = [options objectForKey:@"saveToLibrary"] ? [[options objectForKey:@"saveToLibrary"] boolValue] : YES;

    NSString *stringOutputFileType = Nil;
    NSString *outputExtension = Nil;

    switch (outputFileType) {
        case QUICK_TIME:
            stringOutputFileType = AVFileTypeQuickTimeMovie;
            outputExtension = @".mov";
            break;
        case M4A:
            stringOutputFileType = AVFileTypeAppleM4A;
            outputExtension = @".m4a";
            break;
        case M4V:
            stringOutputFileType = AVFileTypeAppleM4V;
            outputExtension = @".m4v";
            break;
        case MPEG4:
        default:
            stringOutputFileType = AVFileTypeMPEG4;
            outputExtension = @".mp4";
            break;
    }

    // remove file:// from the assetPath if it is there
    assetPath = [[assetPath stringByReplacingOccurrencesOfString:@"file://" withString:@""] mutableCopy];

    // check if the video can be saved to photo album before going further
    if (saveToPhotoAlbum && !UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(assetPath))
    {
        NSString *error = @"Video cannot be saved to photo album";
        [self.commandDelegate sendPluginResult:[CDVPluginResult resultWithStatus:CDVCommandStatus_ERROR messageAsString:error ] callbackId:command.callbackId];
        return;
    }

    NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *tempVideoPath =[NSString stringWithFormat:@"%@/%@%@", docDir, videoFileName, @".mov"];
    NSData *videoData = [NSData dataWithContentsOfFile:assetPath];
    [videoData writeToFile:tempVideoPath atomically:NO];

    AVURLAsset *avAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:tempVideoPath] options:nil];
    NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:avAsset];

    if ([compatiblePresets containsObject:AVAssetExportPresetLowQuality])
    {
        AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]initWithAsset:avAsset presetName: presetName];
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        NSString *videoPath = [NSString stringWithFormat:@"%@/%@%@", [paths objectAtIndex:0], videoFileName, outputExtension];

        exportSession.outputURL = [NSURL fileURLWithPath:videoPath];
        exportSession.outputFileType = stringOutputFileType;
        exportSession.shouldOptimizeForNetworkUse = optimizeForNetworkUse;

        NSLog(@"videopath of your file: %@", videoPath);

        if (videoDuration)
        {
            int32_t preferredTimeScale = 600;
            CMTime startTime = CMTimeMakeWithSeconds(0, preferredTimeScale);
            CMTime stopTime = CMTimeMakeWithSeconds(videoDuration, preferredTimeScale);
            CMTimeRange exportTimeRange = CMTimeRangeFromTimeToTime(startTime, stopTime);
            exportSession.timeRange = exportTimeRange;
        }

        [exportSession exportAsynchronouslyWithCompletionHandler:^{
            switch ([exportSession status]) {
                case AVAssetExportSessionStatusCompleted:
                    if (saveToPhotoAlbum) {
                        UISaveVideoAtPathToSavedPhotosAlbum(videoPath, self, nil, nil);
                    }
                    NSLog(@"Export Complete %d %@", exportSession.status, exportSession.error);
                    [self.commandDelegate sendPluginResult:[CDVPluginResult resultWithStatus:CDVCommandStatus_OK messageAsString:videoPath] callbackId:command.callbackId];
                    break;
                case AVAssetExportSessionStatusFailed:
                    NSLog(@"Export failed: %@", [[exportSession error] localizedDescription]);
                    [self.commandDelegate sendPluginResult:[CDVPluginResult resultWithStatus:CDVCommandStatus_ERROR messageAsString:[[exportSession error] localizedDescription]] callbackId:command.callbackId];
                    break;
                case AVAssetExportSessionStatusCancelled:
                    NSLog(@"Export canceled");
                    break;
                default:
                    NSLog(@"Export default in switch");
                    break;
            }
        }];
    }

}

如何在cordova插件中实现AVAssetWriter？

NSDictionary *settings = @{AVVideoCodecKey:AVVideoCodecH264,
                           AVVideoWidthKey:@(video_width),
                           AVVideoHeightKey:@(video_height),
                           AVVideoCompressionPropertiesKey:
                               @{AVVideoAverageBitRateKey:@(desired_bitrate),
                                 AVVideoProfileLevelKey:AVVideoProfileLevelH264Main31, /* Or whatever profile & level you wish to use */
                                 AVVideoMaxKeyFrameIntervalKey:@(desired_keyframe_interval)}};

AVAssetWriterInput* writer_input = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:settings];

我真的不需要灵活的解决方案，硬编码很好。我不是一个真正的Object-C专家（我发现它是一种非常模糊的语言）

Answer 1

我设法用SDAVAssetExportSession解决了这个问题。接下来，我与作者联系以提交更改。这是代码（必须添加CoreVideo.framework）：

- (void) transcodeVideo:(CDVInvokedUrlCommand*)command
{
    NSDictionary* options = [command.arguments objectAtIndex:0];

    if ([options isKindOfClass:[NSNull class]]) {
        options = [NSDictionary dictionary];
    }

    NSString *assetPath = [options objectForKey:@"fileUri"];
    NSString *videoFileName = [options objectForKey:@"outputFileName"];

    CDVQualityType qualityType = ([options objectForKey:@"quality"]) ? [[options objectForKey:@"quality"] intValue] : LowQuality;

    NSString *presetName = Nil;

    switch(qualityType) {
        case HighQuality:
            presetName = AVAssetExportPresetHighestQuality;
            break;
        case MediumQuality:
        default:
            presetName = AVAssetExportPresetMediumQuality;
            break;
        case LowQuality:
            presetName = AVAssetExportPresetLowQuality;
    }

    CDVOutputFileType outputFileType = ([options objectForKey:@"outputFileType"]) ? [[options objectForKey:@"outputFileType"] intValue] : MPEG4;

    BOOL optimizeForNetworkUse = ([options objectForKey:@"optimizeForNetworkUse"]) ? [[options objectForKey:@"optimizeForNetworkUse"] intValue] : NO;

    float videoDuration = [[options objectForKey:@"duration"] floatValue];

    BOOL saveToPhotoAlbum = [options objectForKey:@"saveToLibrary"] ? [[options objectForKey:@"saveToLibrary"] boolValue] : YES;

    NSString *stringOutputFileType = Nil;
    NSString *outputExtension = Nil;

    switch (outputFileType) {
        case QUICK_TIME:
            stringOutputFileType = AVFileTypeQuickTimeMovie;
            outputExtension = @".mov";
            break;
        case M4A:
            stringOutputFileType = AVFileTypeAppleM4A;
            outputExtension = @".m4a";
            break;
        case M4V:
            stringOutputFileType = AVFileTypeAppleM4V;
            outputExtension = @".m4v";
            break;
        case MPEG4:
        default:
            stringOutputFileType = AVFileTypeMPEG4;
            outputExtension = @".mp4";
            break;
    }

    // remove file:// from the assetPath if it is there
    assetPath = [[assetPath stringByReplacingOccurrencesOfString:@"file://" withString:@""] mutableCopy];

    // check if the video can be saved to photo album before going further
    if (saveToPhotoAlbum && !UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(assetPath))
    {
        NSString *error = @"Video cannot be saved to photo album";
        [self.commandDelegate sendPluginResult:[CDVPluginResult resultWithStatus:CDVCommandStatus_ERROR messageAsString:error ] callbackId:command.callbackId];
        return;
    }

    NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *tempVideoPath =[NSString stringWithFormat:@"%@/%@%@", docDir, videoFileName, @".mov"];
    NSData *videoData = [NSData dataWithContentsOfFile:assetPath];
    [videoData writeToFile:tempVideoPath atomically:NO];

    AVURLAsset *avAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:tempVideoPath] options:nil];
    NSArray *compatiblePresets = [AVAssetExportSession exportPresetsCompatibleWithAsset:avAsset];

    SDAVAssetExportSession *encoder = [SDAVAssetExportSession.alloc initWithAsset:avAsset];

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *videoPath = [NSString stringWithFormat:@"%@/%@%@", [paths objectAtIndex:0], videoFileName, outputExtension];

    encoder.outputFileType = stringOutputFileType;
    encoder.outputURL = [NSURL fileURLWithPath:videoPath];
    encoder.shouldOptimizeForNetworkUse = optimizeForNetworkUse;
    encoder.videoSettings = @
    {
    AVVideoCodecKey: AVVideoCodecH264,
    AVVideoWidthKey: @1280,
    AVVideoHeightKey: @720,
    AVVideoCompressionPropertiesKey: @
        {
        AVVideoAverageBitRateKey: @1200000,
        AVVideoProfileLevelKey: AVVideoProfileLevelH264High40,
        },
    };
    encoder.audioSettings = @
    {
    AVFormatIDKey: @(kAudioFormatMPEG4AAC),
    AVNumberOfChannelsKey: @2,
    AVSampleRateKey: @44100,
    AVEncoderBitRateKey: @128000,
    };

    [encoder exportAsynchronouslyWithCompletionHandler:^
     {
         if (encoder.status == AVAssetExportSessionStatusCompleted)
         {
             if (saveToPhotoAlbum) {
                 UISaveVideoAtPathToSavedPhotosAlbum(videoPath, self, nil, nil);
             }
             NSLog(@"Export Complete %d %@", encoder.status, encoder.error);
             [self.commandDelegate sendPluginResult:[CDVPluginResult resultWithStatus:CDVCommandStatus_OK messageAsString:videoPath] callbackId:command.callbackId];
         }
         else if (encoder.status == AVAssetExportSessionStatusCancelled)
         {
             NSLog(@"Video export cancelled");
         }
         else
         {
             NSLog(@"Export failed: %@", [[encoder error] localizedDescription]);
             [self.commandDelegate sendPluginResult:[CDVPluginResult resultWithStatus:CDVCommandStatus_ERROR messageAsString:[[encoder error] localizedDescription]] callbackId:command.callbackId];
         }
         /*switch ([encoder status]) {
          case AVAssetExportSessionStatusCompleted:

          break;
          case AVAssetExportSessionStatusFailed:

          break;
          case AVAssetExportSessionStatusCancelled:
          NSLog(@"Export canceled");
          break;
          default:
          NSLog(@"Export default in switch");
          break;
          }*/

     }];
    /*if ([compatiblePresets containsObject:AVAssetExportPresetLowQuality])
     {
     AVAssetExportSession *exportSession = [[AVAssetExportSession alloc]initWithAsset:avAsset presetName: presetName];
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
     NSString *videoPath = [NSString stringWithFormat:@"%@/%@%@", [paths objectAtIndex:0], videoFileName, outputExtension];

     exportSession.outputURL = [NSURL fileURLWithPath:videoPath];
     exportSession.outputFileType = stringOutputFileType;
     exportSession.shouldOptimizeForNetworkUse = optimizeForNetworkUse;

     NSLog(@"videopath of your file: %@", videoPath);

     if (videoDuration)
     {
     int32_t preferredTimeScale = 600;
     CMTime startTime = CMTimeMakeWithSeconds(0, preferredTimeScale);
     CMTime stopTime = CMTimeMakeWithSeconds(videoDuration, preferredTimeScale);
     CMTimeRange exportTimeRange = CMTimeRangeFromTimeToTime(startTime, stopTime);
     exportSession.timeRange = exportTimeRange;
     }

     [exportSession exportAsynchronouslyWithCompletionHandler:^{
     switch ([exportSession status]) {
     case AVAssetExportSessionStatusCompleted:
     if (saveToPhotoAlbum) {
     UISaveVideoAtPathToSavedPhotosAlbum(videoPath, self, nil, nil);
     }
     NSLog(@"Export Complete %d %@", exportSession.status, exportSession.error);
     [self.commandDelegate sendPluginResult:[CDVPluginResult resultWithStatus:CDVCommandStatus_OK messageAsString:videoPath] callbackId:command.callbackId];
     break;
     case AVAssetExportSessionStatusFailed:
     NSLog(@"Export failed: %@", [[exportSession error] localizedDescription]);
     [self.commandDelegate sendPluginResult:[CDVPluginResult resultWithStatus:CDVCommandStatus_ERROR messageAsString:[[exportSession error] localizedDescription]] callbackId:command.callbackId];
     break;
     case AVAssetExportSessionStatusCancelled:
     NSLog(@"Export canceled");
     break;
     default:
     NSLog(@"Export default in switch");
     break;
     }
     }];
     }*/

}

修改Cordova Video Editor的AVAsset中的比特率

1 个答案: