Linux Mint 17.1, Nvidia GTX 580
Short description of error
When using the video sequencer, I discovered that Blender does not seem to handle the pixel format yuvj420p correctly. This results in incorrect color reproduction and output.
As you might know, the pixel format yuv420p (without the 'j') stores the color values between values 16 (black) and 239 (white), while the format yuvj420p utilizes the whole range between 0 and 255. Currently, it seems that Blender incorrectly identifies, or treats, the yuvj420p format as if it was a yuv420p format, thus distorting the colors.
I think this issue matters to many, since yuvj420p is what the GoPro camera delivers, and likely many other consumer digital cameras.
Exact steps for others to reproduce the error
In the video editing environment, import an unmodified GoPro (I have the Hero 4 Black) movie clip with Add->Movie. If you compare the blender output or preview, you will see that the colors look different than if the same movie clip is played back with any video player, such as vlc. It seems to be most obvious in bright, saturated areas.
GoPro movie clips can be sent upon request. If one does not have access to yuvj420p files, another way to expose the error would be to convert an existing yuv420p file to yuvj420p with ffmpeg, and then bring it in to blender, and compare with the original file.
ffmpeg -i INPUT_FILE -acodec copy -vcodec libx264 -pix_fmt:v yuvj420p OUTPUT_FILE.mp4
To check the pixel format an existing movie clip, use ffprobe.