如何使用AVAssetWriter制作缩小尺寸的视频？ [英] How do make a reduced size video using AVAssetWriter?

问题描述

我会制作缩小尺寸的视频，可能是50像素，75像素长。这些是物理方面。

I would make reduced size video, maybe 50 pixel across and 75 pixels for length. Those are the physical dimension.

你如何设定？在视频设计？我认为AVVideoWidthKey和AVVideoHeightKey更适用于我需要的物理尺寸分辨率。

How do you set that? in the videosettings? I think AVVideoWidthKey and AVVideoHeightKey are more for resolution not for physically dimension which what I needed.

NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               AVVideoCodecH264, AVVideoCodecKey,
                               [NSNumber numberWithInt: 320], AVVideoWidthKey,    
                               [NSNumber numberWithInt:480], AVVideoHeightKey,   
                               nil];
AVAssetWriterInput* writerInput = [[AVAssetWriterInput
                                    assetWriterInputWithMediaType:AVMediaTypeVideo
                                    outputSettings:videoSettings] retain

推荐答案

您需要设置视频编解码器参数：

You need to set video codec parameters:

NSDictionary *videoCleanApertureSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                           [NSNumber numberWithInt:320], AVVideoCleanApertureWidthKey,
                                           [NSNumber numberWithInt:480], AVVideoCleanApertureHeightKey,
                                           [NSNumber numberWithInt:10], AVVideoCleanApertureHorizontalOffsetKey,
                                           [NSNumber numberWithInt:10], AVVideoCleanApertureVerticalOffsetKey,
                                            nil];


NSDictionary *videoAspectRatioSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                             [NSNumber numberWithInt:3], AVVideoPixelAspectRatioHorizontalSpacingKey,
                                             [NSNumber numberWithInt:3],AVVideoPixelAspectRatioVerticalSpacingKey,
                                                    nil];



NSDictionary *codecSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               [NSNumber numberWithInt:960000], AVVideoAverageBitRateKey,
                               [NSNumber numberWithInt:1],AVVideoMaxKeyFrameIntervalKey,
                               videoCleanApertureSettings, AVVideoCleanApertureKey,
                               //videoAspectRatioSettings, AVVideoPixelAspectRatioKey,
                               //AVVideoProfileLevelH264Main30, AVVideoProfileLevelKey,
                               nil];





NSString *targetDevice = [[UIDevice currentDevice] model];

NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               AVVideoCodecH264, AVVideoCodecKey,
                               codecSettings,AVVideoCompressionPropertiesKey,
                               [NSNumber numberWithInt:320], AVVideoWidthKey,
                               [NSNumber numberWithInt:480], AVVideoHeightKey,
                               nil];

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