speeding up x264 encoding (C++ code with libavcodec)

Question

I am trying to capture windows screen (continuous screen shots) and encode them into x264. For that I am using avcodec_encode_video2 function available with libavcodec. However, it takes a huge amount of time. The time fluctuates between 25 – 1800 milliseconds for encoding individual frames.

I tried tried both 1080p and 720p with video recording on screen.

These are the settings I am using. This was tested on Windows 7, win32 release build with 4 GB of RAM.

bit_rate = 2000, width = 1920, height = 1080 qmin = 0, qmax = 0, max_b_frames = 0, frame_rate = 25, pixel_format = YUV 4:4:4. The remaining settings are default which are fetched using avcodec_get_context_defaults3().

Sample data(in milliseconds) for 20 frames (consecutive and chosen randomly) in a set of 250 frames. { 121, 106, 289, 126, 211, 30, 181, 58, 213, 34, 245, 50, 56, 364, 247, 171, 254, 83, 82, 229 }

For the application it is a must that it captures at least at 15 fps. Can someone help out to tell whether any options can be used to improve the frame rate. I need to encode lossless, but I am open to some file size increase.

Thanks in advance.

Answer 1

The Simple solution to the problem is to use libx264 directly rather than going through avcodec. This allows you to have a better control over x264 and thereby, the encoding speed improves. With avcodec, it also does some not needed processing. That can be avoided with libx264.

Moral of the story, use the x264 API directly.