[Libav-user] No accelerated colorspace conversion - What does it mean?

[Paul B Mahol]

On 4/20/13, Gary Overall <goverall at hotmail.com> wrote:
> I receive the following message:
>
>
>
>
>
>
>
> [swscaler @ 0x8b0de00] No accelerated colorspace conversion found from
> yuv420p to rgb24.
> when issuing:
>
>
>
>
>
>
>
>         sws_ctx =
>         sws_getContext
>         (
>          pCodecCtx->width,
>          pCodecCtx->height,
>          pCodecCtx->pix_fmt,
>          pCodecCtx->width,
>          pCodecCtx->height,
>          PIX_FMT_RGB24,
>          SWS_BILINEAR,
>          NULL,
>          NULL,
>          NULL
>          );
> in my iOS app when running the iPhone or IPad simulator.  I am decoding and
> h264 video. I had to turn off assembler optimizations (--disable-asm) in my
> configure script for the i386 compile in order to avoid the following error
> during the make of the i386 libraries:
> cc1: error in backend: Ran out of registers during register allocation!make:
> *** [libavcodec/h264_cabac.o] Error 1

This is bug that should be reported if it's not already reported.
Additionally it should be possible to disable optimizations only for
certain files.

> My questions:
> 1) Does "No accelerated colorspace conversion found" mean that
> there were no assembler optimizations?

It means there where no assembler optimizations enabled at compilation.

> 2) If so, is there a way to make it
> run without assembler optimizations? ( I don't mind if it is slow on the
> simulator)

You are already running without optimizations.

> 3) If so again, how do I avoid the error when attempting the make
> with assembler optimizations?

If assembler optimizations are enabled error will not be displayed.

> 4) Most importantly, am I even on the right
> path to solving this problem?
> I truly appreciate your kind response:
> Here is a copy of my configure command for the i386 build.
>
> ./configure \--prefix=i386 \--disable-programs \--enable-avresample
> \--disable-bzlib --disable-doc --enable-pic --disable-zlib
> --enable-decoder=h264 --enable-demuxer=h264 --enable-parser=h264
> --disable-libschroedinger --disable-libspeex --disable-libtheora
> --disable-libvorbis --disable-libvpx \--enable-cross-compile
> \--sysroot="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk"
> \--target-os=darwin
> \--cc="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc"
> \--extra-cflags="-arch i386" \--extra-ldflags="-arch i386 -isysroot
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk"
> \--arch=i386 \--cpu=i386 \--enable-pic \--disable-asm \
>
  		 	   		
--disable-asm means no asm optimizations will be compiled in, thus
that warning happens.