Convert raw image buffer into JPEG using LIBAVCODEC - c

Question

I have a raw image buffer (in memory) captured from a camera that I want to convert into JPEG (for reducing size). The problem is that saving these images into .pgm format results into a huge file size that I can't afford due to the memory limitations and latency involved in saving a huge file of this size (a constraint in the application I am working on).
I want to know how do I compress/encode an image buffer into .jpg format using LIBAVCODEC? My image capture code is in C.

Answer 1

this code works with YUV raw images. I got segfault trying to encode an RGB raw image. but you can use swscale() to convert RGB to YUV
int main()
{
int ret;
AVFrame *frame;
AVPacket pkt;
av_register_all();
AVCodec* codec = avcodec_find_encoder(AV_CODEC_ID_MJPEG);
if (!codec)
{
printf("Codec not found\n");
exit(1);
}
AVCodecContext* c = avcodec_alloc_context3(codec);
if (!c)
{
printf("Could not allocate video codec context\n");
exit(1);
}
c->bit_rate = 400000;
c->width = 320;
c->height = 200;
c->time_base= (AVRational){1,25};
c->pix_fmt = AV_PIX_FMT_YUVJ420P;
if (avcodec_open2(c, codec, NULL) < 0)
{
printf("Could not open codec\n");
exit(1);
}
frame = avcodec_alloc_frame();
if (!frame)
{
printf("Could not allocate video frame\n");
exit(1);
}
frame->format = c->pix_fmt;
frame->width = c->width;
frame->height = c->height;
ret = av_image_alloc(frame->data, frame->linesize, c->width, c->height, c->pix_fmt, 32);
if (ret < 0)
{
printf("Could not allocate raw picture buffer\n");
exit(1);
}
av_init_packet(&pkt);
pkt.data = NULL;
pkt.size = 0;
/* prepare a dummy image */
/* Y */
for(int y=0;y<c->height;y++) {
for(int x=0;x<c->width;x++) {
frame->data[0][y * frame->linesize[0] + x] = x + y;
}
}
/* Cb and Cr */
for(int y=0;y<c->height/2;y++) {
for(int x=0;x<c->width/2;x++) {
frame->data[1][y * frame->linesize[1] + x] = 128 + y;
frame->data[2][y * frame->linesize[2] + x] = 64 + x;
}
}
frame->pts = 1;
int got_output = 0;
ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
if (ret < 0)
{
printf("Error encoding frame\n");
exit(1);
}
if (got_output)
{
printf("got frame\n");
FILE* f = fopen("x.jpg", "wb");
fwrite(pkt.data, 1, pkt.size, f);
av_free_packet(&pkt);
}
avcodec_close(c);
av_free(c);
av_freep(&frame->data[0]);
avcodec_free_frame(&frame);
printf("\n");
return 0;
}