Decoding video pixel data in C++ using FFmpeg (Part 2)

This part of the livestream builds on what we've done before. I successfully decode a video frame, but the pixel data is stored in YUV as opposed to RGB. So in this short tutorial I change the color format using libswscale to RGB.

[zacharynicoll]

Such an awesome tutorial, along with the previous video. So detailed yet so concise. Absolute legend.

[sephjfox]

This tutorial is awesome! I wish I had found this video before. Doing this without context is like falling down a staircase in the dark.

[ytbTheogr]

Awesome work dude. wish you could do more ffmpeg tutorials!

[adamburke]

Great video overall! Your simple explanation of the human visual system is generally correct when you say we see luminance better than color. However, more specifically, we are more sensitive to luminance *spatially*.


It’s unfortunate the term YUV is used in FFMPEG as it is an outdated term from the analog days where Y’CbCr is digital.

[babymetalsheets]

13:11 why do we need 4 buffers, while we dont use 3 of them? I have not found proper docs/examples yet, but i got rid of them and there is no difference between 1, 2, 7, 12... buffers

[thisiscentralcontrol]

You would be much better off uploading the YUV frames to the GPU and then writing a shader to convert to RGB for final display.Not only do you not need to use loads of CPU resources to handle the conversion, but also you save PCIe bandwidth, not to mention the fact that GPUs handle upload of 2BPP formats a lot better than 3BPP pixel formats.

[peacehappinessmoment]

@Bartholomew
How do i save these
*width_out = av_frame->width;
*height_out = av_frame->height;
*data_out = data;
in png file.

I tried but the image is full black??
FILE *pFile;
pFile = fopen("frame.png", "wb");

if (!pFile) {
ALOG("Couldn't get pFile\n");
return false;
}
fprintf(pFile, "P6\n%d %d\n255\n", av_frame->width, av_frame->height);
for (y = 0; y < av_frame->height; y++)
fwrite(data, 1, av_frame->width * 3, pFile);
fclose(pFile);

[amadeokusch]

hey thanks for the tutorial. i've been getting problems decode h264 to raw rgb without unwanted color or brightness shifting, do you know how to do it?

[shubhampancholi]

Can you please decode video an audio both in c++