AVAssetWriter 如何创建没有压缩的 mov 视频？答案

【问题标题】：AVAssetWriter How to create mov video with no compression?AVAssetWriter 如何创建没有压缩的 mov 视频？
【发布时间】：2015-08-01 21:37:14
【问题描述】：

我正在从一组图像创建视频。我工作的目的是创建一个没有压缩的 .mov 视频。我在开发人员库中看到它存在一个键“AVVideoCompressionPropertiesKey”，但我不知道如何使用此键指定不压缩。

你能帮帮我吗？

这是我的示例代码：

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

NSDictionary *codecSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               [NSNumber numberWithInt:960000], AVVideoAverageBitRateKey,
                               [NSNumber numberWithInt:1],AVVideoMaxKeyFrameIntervalKey,
                               videoCleanApertureSettings, AVVideoCleanApertureKey,
                               nil];


NSDictionary *videoOutputSettings = [NSDictionary dictionaryWithObjectsAndKeys:AVVideoCodecH264, AVVideoCodecKey,codecSettings,AVVideoCompressionPropertiesKey, [NSNumber numberWithInt:size.width], AVVideoWidthKey,
                                     [NSNumber numberWithInt:size.height], AVVideoHeightKey, nil];

self.videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoOutputSettings];

【问题讨论】：

标签： ios compression avfoundation avassetwriter

【解决方案1】：

尝试使用 AVVideoCodecJPEG 并将 AVVideoQualityKey 值设置为 NSNumber 1.0。另一种方法是指定 H264，将比特率设置为非常高的值，并将关键帧间隔指定为 1（即所有关键帧）。

【讨论】：

【解决方案2】：

该键不是用于禁用压缩，而是为某些编解码器指定特定的压缩值，例如 jpg 或 h264 .I.e.

    [videoSettings addEntriesFromDictionary:[NSDictionary dictionaryWithObjectsAndKeys:
                                                 AVVideoCodecH264, AVVideoCodecKey,
                                                 nil]];

        NSMutableDictionary* videoCompressionSettings = [NSMutableDictionary dictionary];

        if ([[Preferences instance] recordingH264Keyframes] > 0) {
            [videoCompressionSettings addEntriesFromDictionary:[NSDictionary dictionaryWithObjectsAndKeys:
                                                     [NSNumber numberWithInt:[[Preferences instance] recordingH264Keyframes]], AVVideoMaxKeyFrameIntervalKey,
                                                     nil]];
        }

        if ([[Preferences instance] recordingH264Bitrate] > 0) {
            [videoCompressionSettings addEntriesFromDictionary:[NSDictionary dictionaryWithObjectsAndKeys:
                                                     [NSNumber numberWithInt:[[Preferences instance] recordingH264Bitrate]*1000], AVVideoAverageBitRateKey,
                                                     nil]];
        }

        if ([videoCompressionSettings count]) {
            [videoSettings addEntriesFromDictionary:[NSDictionary dictionaryWithObjectsAndKeys:videoCompressionSettings,AVVideoCompressionPropertiesKey,nil]];
        }

【讨论】：

【解决方案3】：

ProRes4444 视频编解码器是 Apple 提供的最接近未压缩编解码器的产品。此编解码器不适用于 iOS 上仅用于编写视频内容的 OS X。

无法在 iOS 上导出未压缩的视频内容。

【讨论】：