swscaler警告:使用不推荐使用的像素格式

Question

我想在使用以下代码将视频帧转换为opengl纹理之前对其进行颜色空间转换:

struct SwsContext * pSwsCtx = sws_getCachedContext(NULL,width, height, codec->pix_fmt, width, height, AV_PIX_FMT_RGBA, SWS_POINT, NULL, NULL, NULL);

每次调用sws_getCachedContext()函数时,都会收到以下警告:

[swscaler @ 0x10506fa00] deprecated pixel format used, make sure you did set range correctly

这是我的ffmpeg输出版本信息:

ffmpeg version 2.2 Copyright (c) 2000-2014 the FFmpeg developers
  built on Mar 26 2014 15:29:01 with Apple LLVM version 5.1 (clang-503.0.38) (based on LLVM 3.4svn)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --enable-vda --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid
  libavutil      52. 66.100 / 52. 66.100
  libavcodec     55. 52.102 / 55. 52.102
  libavformat    55. 33.100 / 55. 33.100
  libavdevice    55. 10.100 / 55. 10.100
  libavfilter     4.  2.100 /  4.  2.100
  libavresample   1.  2.  0 /  1.  2.  0
  libswscale      2.  5.102 /  2.  5.102
  libswresample   0. 18.100 /  0. 18.100
  libpostproc    52.  3.100 / 52.  3.100
Hyper fast Audio and Video encoder

有任何想法禁用此警告吗？如何正确设置颜色范围？

Answer 1

您似乎正在尝试阅读AV_PIX_FMT_YUVJXXXP已弃用的帧(请参阅libav doc).您可以使用此变通方法来管理它:

AVPixelFormat pixFormat;
switch (_videoStream->codec->pix_fmt) {
case AV_PIX_FMT_YUVJ420P :
    pixFormat = AV_PIX_FMT_YUV420P;
    break;
case AV_PIX_FMT_YUVJ422P  :
    pixFormat = AV_PIX_FMT_YUV422P;
    break;
case AV_PIX_FMT_YUVJ444P   :
    pixFormat = AV_PIX_FMT_YUV444P;
    break;
case AV_PIX_FMT_YUVJ440P :
    pixFormat = AV_PIX_FMT_YUV440P;
    break;
default:
    pixFormat = _videoStream->codec->codec->pix_fmts;
    break;
}

Answer 2

自问这个问题以来已经很长时间了，但是当我遇到相同的问题时，我看着它并试图找到第二部分的答案（如何正确设置颜色范围？）。我扩展了托马斯·阿尤布的答案：

AVCodecContext* pCodecCtx = _videoStream->codec;
AVPixelFormat pixFormat;
switch (pCodecCtx->pix_fmt)
  {
    case AV_PIX_FMT_YUVJ420P:
      pixFormat = AV_PIX_FMT_YUV420P;
      break;
    case AV_PIX_FMT_YUVJ422P:
      pixFormat = AV_PIX_FMT_YUV422P;
      break;
    case AV_PIX_FMT_YUVJ444P:
      pixFormat = AV_PIX_FMT_YUV444P;
      break;
    case AV_PIX_FMT_YUVJ440P:
      pixFormat = AV_PIX_FMT_YUV440P;
      break;
    default:
      pixFormat = pCodecCtx->pix_fmt;
  }
// initialize SWS context for software scaling
SwsContext *swsCtx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pixFormat, pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_RGB24, SWS_BILINEAR, NULL, NULL, NULL);
// change the range of input data by first reading the current color space and then setting it's range as yuvj.
int dummy[4];
int srcRange, dstRange;
int brightness, contrast, saturation;
sws_getColorspaceDetails(swsCtx, (int**)&dummy, &srcRange, (int**)&dummy, &dstRange, &brightness, &contrast, &saturation);
const int* coefs = sws_getCoefficients(SWS_CS_DEFAULT);
srcRange = 1; // this marks that values are according to yuvj
sws_setColorspaceDetails(swsCtx, coefs, srcRange, coefs, dstRange,
                               brightness, contrast, saturation);

范围是什么？YUV像素格式的值范围为：Y 16..235，UV 16..240。YUVJ扩展了一个，所有YUV都为0 ... 255。

srcRange = 1

强制libav使用扩展的输入数据范围。如果您未在范围内进行任何更改，则可能只会遇到夸大的对比度。它仍应将输入数据缩放到RGB颜色空间。