[Libav-user] get RGB values from ffmpeg frame
Malik Cissé
mc at enciris.com
Tue Nov 20 12:30:30 CET 2012
Hi Navin,
Also YUV4:2:0 in BMP does not seem feasible (sorry for my previous statement).
One think you can do too is use ffmpeg in a system call in your code.
This is very versatile (you need to replace 422 by 420 though)
char ffmpegString[256];//should be plenty
char fmt[] = "bmp"; //bmp, jpg, png, pgm etc...
sprintf(ffmpegString, "ffmpeg.exe -s %dx%d -vcodec rawvideo -f rawvideo -pix_fmt uyvy422 -i raw_uyvy422.yuv -f image2 raw_uyvy422.%s",RawWidth, RawHeight, fmt);
system(ffmpegString);
Malik Cisse
-----Original Message-----
From: libav-user-bounces at ffmpeg.org [mailto:libav-user-bounces at ffmpeg.org] On Behalf Of Navin
Sent: 20 November 2012 12:09
To: libav-user at ffmpeg.org
Subject: Re: [Libav-user] get RGB values from ffmpeg frame
Hey thanks everyone! Still trying/struggling with the code sent by Malik because avcodec_decode_video is deprecated.
Thought I'd post the entire code here for anyone who could help or for anyone who needs such code in future. This is the corrected version of ffmpeg's tutorial02, with SDL added to it too.
Problems are:
1. Since I was facing trouble with RGB, I thought I'd use SDL to output the frames as bitmaps, but although I could store the bitmap in an area in memory, it threw an exception when I tried extracting it out of memory.
2. Besides, when at least trying to output the bitmap to hard disk, I'm unable to output it unless SDL_DisplayYUVOverlay(bmp, &rect); is called (and I don't want to call it because I don't want the video to be displayed. I just want the bitmap to be output).
3. Main problem is still with extracting RGB, so would be grateful for any help. If not RGB, then at least with question 1 (how to store and extract the BMP from SDL memory).
The code:
extern "C"
{
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
}
#include<iostream>
#include <SDL.h>
#include <SDL_thread.h>
#include "SDL_opengl.h"
#include <gl/gl.h>
#include <gl/glu.h>
//#ifdef __MINGW32__
#undef main /* Prevents SDL from overriding main() */
//#endif
#include <stdio.h>
//------------------------
// These functions should not be used except from pointers in a RWops
static int myseekfunc(SDL_RWops *context, int offset, int whence) {
SDL_SetError("Can't seek in this kind of RWops"); return(-1); }
static int myreadfunc(SDL_RWops *context, void *ptr, int size, int
maxnum) { memset(ptr,0,size*maxnum); return(maxnum); }
static int mywritefunc(SDL_RWops *context, const void *ptr, int size,
int num) { return(num); }
static int myclosefunc(SDL_RWops *context)
{
if(context->type != 0xdeadbeef) { SDL_SetError("Wrong kind of RWops
for myclosefunc()"); return(-1); }
free(context->hidden.unknown.data1);
SDL_FreeRW(context);
return(0);
}
// Note that this function is NOT static -- we want it directly callable
from other source files
SDL_RWops *MyCustomRWop()
{
SDL_RWops *c=SDL_AllocRW();
if(c==NULL) return(NULL);
c->seek =myseekfunc;
c->read =myreadfunc;
c->write=mywritefunc;
c->close=myclosefunc;
c->type =0xdeadbeef;
printf("deadbeef=%d\n",c->type);
c->hidden.unknown.data1=malloc(100000);
return(c);
}
int main(int argc, char *argv[])
{
AVFormatContext *pFormatCtx = NULL;
int i, videoStream;
AVCodecContext *pCodecCtx = NULL;
AVCodec *pCodec = NULL;
AVFrame *pFrame = NULL;
AVPacket packet;
int frameFinished;
//float aspect_ratio;
AVDictionary *optionsDict = NULL;
struct SwsContext *sws_ctx = NULL;
SDL_Overlay *bmp = NULL;
SDL_Surface *screen = NULL;
SDL_Surface *screen2 = NULL;
SDL_Surface *rgbscreen = NULL;
SDL_Rect rect;
SDL_Event event;
if(argc < 2) { fprintf(stderr, "Usage: test.exe <videofile>\n");
exit(1); }
// Register all formats and codecs
av_register_all();
if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
exit(1); }
// Open video file
if(avformat_open_input(&pFormatCtx, argv[1], NULL, NULL)!=0)
return -1; // Couldn't open file
// Retrieve stream information
if(avformat_find_stream_info(pFormatCtx, NULL)<0) return -1; //
Couldn't find stream information
// Dump information about file onto standard error
//av_dump_format(pFormatCtx, 0, argv[1], 0);
// Find the first video stream
videoStream=-1;
for(i=0; i<pFormatCtx->nb_streams; i++)
if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) {
videoStream=i; break; }
if(videoStream==-1) return -1; // Didn't find a video stream
// Get a pointer to the codec context for the video stream
pCodecCtx=pFormatCtx->streams[videoStream]->codec;
// Find the decoder for the video stream
pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
if(pCodec==NULL) { fprintf(stderr, "Unsupported codec!\n");
return -1;} // Codec not found
// Open codec
if(avcodec_open2(pCodecCtx, pCodec, &optionsDict) < 0) return -1;
// Could not open codec
// Allocate video frame
pFrame = avcodec_alloc_frame();
#if defined(TRIAL)
int width1 = pCodecCtx->width, height1 = pCodecCtx->height, width2
= pCodecCtx->width, height2 = pCodecCtx->height;
struct SwsContext *resize = sws_getContext(width1, height1,
PIX_FMT_YUV420P, width2, height2, PIX_FMT_RGB24, SWS_BICUBIC, NULL,
NULL, NULL);
AVFrame* frame1 = avcodec_alloc_frame(); // this is your original frame
AVFrame* frame2 = avcodec_alloc_frame();
int num_bytes = avpicture_get_size(PIX_FMT_RGB24, width2, height2);
uint8_t* frame2_buffer = (uint8_t *) av_malloc(num_bytes *
sizeof(uint8_t));
#endif
// Make a screen to put our video
#ifndef __DARWIN__
screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height,
0, 0);
#else
screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height,
24, 0);
#endif
if(!screen) { fprintf(stderr, "SDL: could not set video mode -
exiting\n"); exit(1); }
// Allocate a place to put our YUV image on that screen
bmp = SDL_CreateYUVOverlay(pCodecCtx->width,
pCodecCtx->height, SDL_YV12_OVERLAY, screen);
sws_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height,
pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height,
PIX_FMT_YUV420P, SWS_BILINEAR, NULL, NULL, NULL );
// Read frames and save first five frames to disk
i=0;
while(av_read_frame(pFormatCtx, &packet) >= 0)
{
// Is this a packet from the video stream?
if(packet.stream_index==videoStream)
{
// Decode video frame
avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
// Did we get a video frame?
if(frameFinished)
{
#if defined(TRIAL)
avpicture_fill((AVPicture*) frame2, frame2_buffer,
PIX_FMT_RGB24, width2, height2);
printf("data = %d \n",frame2->data[0]);
printf("linesize = %d %d %d\n",frame2->linesize[0],
frame2->linesize[1], frame2->linesize[2]);
printf("width = %d\n", pCodecCtx->width);
printf("height = %d\n", pCodecCtx->height);
std::cin.get();
int linesize = frame2->linesize[0];
for(int xx = 0; xx < (linesize * width1)-1; xx += 3)
{
int r = frame2->data[0][xx];//int r = frame2->data[0][xx];
int g = frame2->data[0][xx+1];
int b = frame2->data[0][xx+2];
printf("xx=%d r=%d, g=%d, b=%d \n",xx, r,
g, b);
}
printf("frame%d done----------------",i++);
//for(int xx = 0; xx < width1; xx = xx + 3)
//{
// for(int yy = 0; yy < height1; ++yy)
// {
// //int p = xx*3 + yy*frame2->linesize[0];
// //int p = xx * 3 + yy * linesize;
// printf("yy=%d xx=%d",yy,xx);
// int p = yy * linesize + xx;
// printf("p=%d\n",p);
// int r = frame2->data[0][p];
// int g = frame2->data[0][p+1];
// int b = frame2->data[0][p+2];
// printf("[r=%d, g=%d, b=%d ]\n", r, g, b);
// }//for
//}//for
// frame1 should be filled by now (eg using avcodec_decode_video)
sws_scale(resize, frame1->data, frame1->linesize, 0, height1,
frame2->data, frame2->linesize);
#endif
SDL_LockYUVOverlay(bmp);//-----------lock
AVPicture pict;
pict.data[0] = bmp->pixels[0];
pict.data[1] = bmp->pixels[2];
pict.data[2] = bmp->pixels[1];
pict.linesize[0] = bmp->pitches[0];
pict.linesize[1] = bmp->pitches[2];
pict.linesize[2] = bmp->pitches[1];
// Convert the image into YUV format that SDL uses
sws_scale( sws_ctx, (uint8_t const * const *)pFrame->data,
pFrame->linesize, 0, pCodecCtx->height, pict.data, pict.linesize );
SDL_UnlockYUVOverlay(bmp);//-----------unlock
rect.x = 0;
rect.y = 0;
rect.w = pCodecCtx->width;
rect.h = pCodecCtx->height;
SDL_DisplayYUVOverlay(bmp, &rect);
//printf("sizeof screen = %d\n",sizeof(*screen));
if (++i != 0)
{
char numberbuffer [33], str[80]; strcpy (str, "bitmap");
strcat (str, itoa(i, numberbuffer, 10)); strcat (str, ".bmp");//file for
storing image
//---------this saves it as a bitmap to filestream. But now
how to extract it?
//SDL_RWops *filestream = MyCustomRWop();//SDL_AllocRW();
//SDL_SaveBMP_RW (screen, filestream, i);
//screen2 = SDL_LoadBMP_RW(filestream,1);//LOADING IS THE
PROBLEM HERE. DON'T KNOW WHY
//filestream->close;
//SDL_SaveBMP(screen2, str);
SDL_SaveBMP(screen, str);//WORKS: saves frame to a file as
a bitmap
}
}//if(frameFinished)
}//if
// Free the packet that was allocated by av_read_frame
av_free_packet(&packet);
SDL_PollEvent(&event);
switch(event.type)
{
case SDL_QUIT:
SDL_Quit();
exit(0);
break;
default:
break;
}//switch
}//while
av_free(pFrame);// Free the YUV frame
avcodec_close(pCodecCtx);// Close the codec
avformat_close_input(&pFormatCtx);// Close the video file
return 0;
}//main
Nav
On 11/20/2012 3:38 PM, Carl Eugen Hoyos wrote:
> Navin<nkipe at ...> writes:
>
>> I have been through many websites, but they either use
>> img_convert (which doesn't work) or sws_scale, which
>> crashes when I try to use it with RGB.
> I may miss something, but I guess this is the important
> problem you should work on (see doc/examples).
>
> Possibly unrelated:
> In your source code, I did not find information which
> decoder you are using.
> Some decoders (everything mpeg-related) output yuv, and
> if you want the data in rgb, you have to convert it
> (using the sofware scaler), others (some lossless formats)
> output rgb, that may already be the data you want.
>
> Carl Eugen
>
> _______________________________________________
> Libav-user mailing list
> Libav-user at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/libav-user
>
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