[Libav-user] Mapping / converting QTCapture's to FFmpeg's pixel format

[Michel Marchand]

I'm no expert in ffmpeg but one in broadcast video and normally YCrCb 422
is not full range that is Y ranges from16 to 235 and Cr/Cb are signed and
range from 16 to 240 (128 being 0). The Full range term may use the full
0-255 range and that could cause problems but not sure...

On Mon, Feb 4, 2013 at 7:31 PM, Brad O'Hearne <brado at bighillsoftware.com>wrote:

> Carl,
>
> Thanks for the reply. I've tried both PIX_FMT_NV12 and PIX_FMT_NV21 (in
> fact, those were the ones I originally thought would work based on
> description). However, when I use either of those formats in place of
> PIX_FMT_YUV420P in the following line of code:
>
> int returnVal = avpicture_fill((AVPicture*)avFrame,
> frameBufferBaseAddress, PIX_FMT_YUV420P, width, height);
>
> then while it executes the avpicture_fill line successfully, the
> subsequent line of code
>
> returnVal = avcodec_encode_video2(_videoStream->codec, &avPacket,
> avFrame, &gotPacket);
>
> crashes the whole app with an EXC_BAD_ACCESS error --  and there's no
> message of any kind written to the console. I have no idea what is causing
> the crash. Here's the complete block of the code between those two lines:
>
> ...
>  int returnVal = avpicture_fill((AVPicture*)avFrame,
> frameBufferBaseAddress, PIX_FMT_NV21, width, height);
>
>
>     if (returnVal < 0)
>     {
>         if (error)
>         {
>          NSLOG(@"Frame fill failed.");
>         }
>
>
>         return NO;
>     }
>
>     AVPacket avPacket;
>     av_init_packet(&avPacket);
>     avPacket.data = NULL;
>     avPacket.size = 0;
>     int gotPacket;
>
>
>     returnVal = avcodec_encode_video2(_videoStream->codec, &avPacket,
> avFrame, &gotPacket);
> ...
>
> That's been pretty standard for most of the other pixel formats I've
> tried. There have been one or two that didn't crash the app, but had very
> wacky distortions (like half the image being neon green), but most of them
> just crash the app outright.
>
> Ideas?
>
> Brad
>
> On Feb 4, 2013, at 4:55 PM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
>
> Brad O'Hearne <brado at ...> writes:
>
> "Bi-Planar Component Y'CbCr 8-bit 4:2:0, full-range
> (luma=[0,255] chroma=[1,255]). baseAddr points to a
> big-endian CVPlanarPixelBufferInfo_YCbCrBiPlanar struct."
>
> My code (heavily abridged for brevity) hits these high points:
>
> NOTE: frameBufferAddress is a CVImageBufferRef received
> from the QT capture callback:
>
>     int returnVal = avpicture_fill((AVPicture*)avFrame,
> frameBufferBaseAddress, PIX_FMT_YUV420P, width, height);
>
>
> Could "biplanar" point to AV_PIX_FMT_NV12?
> (Or something else that is not AV_PIX_FMT_YUV420P)
>
> Carl Eugen
>
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