Aah.
I mis understood how it worked, sorry. Thanks for pointing that out. I
went back and looked at more examples closely. I now have it working.
Cheers :)
On 14/11/10 04:37, sq.cheng wrote:
Just like my reply for another thread, the keys are the input and output for
sws_scale().
1, nFrame = avcodec_alloc_frame();
avcodec_alloc_frame(), it can NOT know what exactly you want to do.
It don'know you want RGB24 frame, so how it can alloc RGB24 frame?
2 and in sws_scale : the nFrame->data, and nFrame->linesize
here, you can print or dump them to see what are they,
1& 2 are not enough to let sws_scale know what you want.
For output frame, you need to allocate memory for nFrame->data
according to your image, width*height*(24/8)
and you need to give the values of nFrame->linesize[4].
On Sun, Nov 14, 2010 at 8:49 AM, George Smart<[email protected]>wrote:
Hi All,
I am trying to convert from YUV420P to RGB24 with /sws_scale/. The source
video is from an AVI file, via /avcodec_decode_video2()/. I get a
segmentation fault every time, and am at a complete loss. If anyone can
suggest anything I would be greatly appreciative. I have followed various
tutorials and looked at many different examples. I am sure it's a simple
mistake I'm making. My /sws_getContext()/ Call is as follows:
swsC = sws_getContext( pCodecCtx->width, // Source width
pCodecCtx->height, //
Source height
//pFrame->pict_type, //
Source format (maybe PIX_FMT_YUV420P)
pCodecCtx->pix_fmt, // Source
format (maybe PIX_FMT_YUV420P)
pCodecCtx->width, // Dest
width
pCodecCtx->height, // Dest
height
PIX_FMT_RGB24, // Dest
format
SWS_FAST_BILINEAR+SWS_PRINT_INFO, // Transform Type (choose from SWS
FLAGS)
NULL, NULL, NULL); //
Filters& Pointer Setup (NULL chooses defaults for last 3 options)
After checking /swsC/ this is used directly in the /sws_scale()/ call, as
follows:
sws_scale( swsC, // SwsContext -
Setup for scaling
(const uint8_t* const*) pFrame->data, //
Source frame data (cast to required type)
pFrame->linesize, //
Source frame stride
0, //
Source frame slice width (raster, so no width slicing)
pCodecCtx->height, //
Source frame slice height
nFrame->data, //
Dest frame data
nFrame->linesize); //
Dest frame stride
In the above line(s), I get the SEG fault - every time.
Any pointers (no pun intended) would be greatly received. Full Program
Listing, here: http://www.ee.ucl.ac.uk/~zceed42/gs.html<
http://www.ee.ucl.ac.uk/%7Ezceed42/gs.html>
Thanks, Regards,
George Smart.
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