媒体解码器和相机，色彩空间不正确

Question

参考Aegonis的作品1和作品2，我也得到了H.264流，但是颜色不正确。我使用HTC Butterfly进行开发。下面是我的部分代码:

照相机:

parameters.setPreviewSize(width, height);
parameters.setPreviewFormat(ImageFormat.YV12);
parameters.setPreviewFrameRate(frameRate);

MediaCodec:

mediaCodec = MediaCodec.createEncoderByType("video/avc");
MediaFormat mediaFormat = MediaFormat.createVideoFormat("video/avc", 320, 240);
mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, 500000);
mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, 15);
mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420SemiPlanar);
mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 5);   
mediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE); 
mediaCodec.start();   

当使用COLOR_FormatYUV420Planar时，错误显示"[OMX.qcom.video.encoder。avc]不支持颜色格式19，"所以我只能使用"COLOR_FormatYUV420SemiPlanar"。有人知道为什么没有支持吗?

得到它，通过使用:

int colorFormat = 0;
    MediaCodecInfo.CodecCapabilities capabilities = codecInfo.getCapabilitiesForType(mimeType);
    for (int i = 0; i < capabilities.colorFormats.length && colorFormat == 0; i++) {
        int format = capabilities.colorFormats[i];
        Log.e(TAG, "Using color format " + format);           
    }

我们可以有颜色格式21 (COLOR_FormatYUV420SemiPlanar)和2130708361(没有相应的格式)，我认为格式会根据设备而变化。

然后，我尝试了工作1和工作2中建议的颜色变换:

public static byte[] YV12toYUV420PackedSemiPlanar(final byte[] input, final byte[] output, final int width, final int height) {
    /* 
     * COLOR_TI_FormatYUV420PackedSemiPlanar is NV12
     * We convert by putting the corresponding U and V bytes together (interleaved).
     */
    final int frameSize = width * height;
    final int qFrameSize = frameSize/4;
    System.arraycopy(input, 0, output, 0, frameSize); // Y
    for (int i = 0; i < qFrameSize; i++) {
        output[frameSize + i*2] = input[frameSize + i + qFrameSize]; // Cb (U)
        output[frameSize + i*2 + 1] = input[frameSize + i]; // Cr (V)
    }
    return output;
}
public static byte[] YV12toYUV420Planar(byte[] input, byte[] output, int width, int height) {
    /* 
     * COLOR_FormatYUV420Planar is I420 which is like YV12, but with U and V reversed.
     * So we just have to reverse U and V.
     */
    final int frameSize = width * height;
    final int qFrameSize = frameSize/4;
    System.arraycopy(input, 0, output, 0, frameSize); // Y
    System.arraycopy(input, frameSize, output, frameSize + qFrameSize, qFrameSize); // Cr (V)
    System.arraycopy(input, frameSize + qFrameSize, output, frameSize, qFrameSize); // Cb (U)
    return output;
}
public static byte[] swapYV12toI420(byte[] yv12bytes, int width, int height) {
    byte[] i420bytes = new byte[yv12bytes.length];
    for (int i = 0; i < width*height; i++)
        i420bytes[i] = yv12bytes[i];
    for (int i = width*height; i < width*height + (width/2*height/2); i++)
        i420bytes[i] = yv12bytes[i + (width/2*height/2)];
    for (int i = width*height + (width/2*height/2); i < width*height + 2*(width/2*height/2); i++)
        i420bytes[i] = yv12bytes[i - (width/2*height/2)];
    return i420bytes;
}

显然，YV12toYUV420PackedSemiPlanar的颜色变换性能优于其他两个。它相对好一些，但与真实的颜色相比看起来仍然不同。我的代码有问题吗?任何评论将不胜感激。

Answer 1

明白了，现在颜色看起来不错，测试是基于HTC蝴蝶。当将分辨率设置为320x240时，你的颜色变换应该看起来像:

    System.arraycopy(input, 0, output, 0, frameSize);
    for (int i = 0; i < (qFrameSize); i++) {  
        output[frameSize + i*2] = (input[frameSize + qFrameSize + i - 32 - 320]);  
        output[frameSize + i*2 + 1] = (input[frameSize + i - 32 - 320]);            
    }

分辨率为640x480及以上，

System.arraycopy(input, 0, output, 0, frameSize);    
    for (int i = 0; i < (qFrameSize); i++) {  
        output[frameSize + i*2] = (input[frameSize + qFrameSize + i]);  
        output[frameSize + i*2 + 1] = (input[frameSize + i]);   
    } 

对于帧率问题，我们可以使用getSupportedPreviewFpsRange()来检查设备支持的帧率范围:

List<int[]> fpsRange = parameters.getSupportedPreviewFpsRange();
for (int[] temp3 : fpsRange) {
System.out.println(Arrays.toString(temp3));}

以下设置在播放编码后的H.264 ES时正常工作，

parameters.setPreviewFpsRange(29000, 30000);    
//parameters.setPreviewFpsRange(4000,60000);//this one results fast playback when I use the FRONT CAMERA 

Answer 2

在阅读了这个讨论之后，发现了编码帧的更通用的方法在将帧发送到MediaCodec之前，将色度平面对齐2048字节。这是实际的QualComm (OMX.qcom.video.encoder.avc)编码器，我相信HTC蝴蝶有，但仍然不能很好地为所有分辨率工作。根据输出视频，720x480和176x144仍然有色度面错位。同时，避免尺寸不能除以16的分辨率。

转换非常简单:

int padding = 0;
if (mediaCodecInfo.getName().contains("OMX.qcom")) {
  padding = (width * height) % 2048;
}
byte[] inputFrameBuffer = new byte[frame.length];
byte[] inputFrameBufferWithPadding = new byte[padding + frame.length];
ColorHelper.NV21toNV12(frame, inputFrameBuffer, width, height);
# copy Y plane
System.arraycopy(inputFrameBuffer, 0, inputFrameBufferWithPadding, 0, inputFrameBuffer.length);
int offset = width * height;
# copy U and V planes aligned by <padding> boundary
System.arraycopy(inputFrameBuffer, offset, inputFrameBufferWithPadding, offset + padding, inputFrameBuffer.length - offset);