nm
16th May 2012, 17:54
I still dont quite get it here. I need to have a constant rate control (using --fps and --bitrate) so that I get a fair output for comparison. How many frames should I be using to ensure that the encoder can apply the value of fps or bitrate that I enter because right now I got the following message whenever i encode
You'll need about 50 to 100 frames and run two passes:
x264 --bitrate 500 --pass 1 -o output.264 input
x264 --bitrate 500 --pass 2 -o output.264 input
Or perhaps more if you want accurate results with a short clip:
x264 --bitrate 500 --pass 1 -o output.264 input
x264 --bitrate 500 --pass 3 -o output.264 input (--pass 3 is not a typo here!)
x264 --bitrate 500 --pass 3 -o output.264 input
x264 --bitrate 500 --pass 3 -o output.264 input
...
But if three passes isn't accurate enough, fourth isn't going to help. You'll need a longer clip then.
IMO, 8 frames is not enough for any video testing. You need at least a couple seconds at a realistic framerate (10 to 60 fps) for real world video comparisons.
Stream #0: not enough frames to estimate rate; consider increasing probesize
That message comes from libav/FFmpeg which demuxes and decodes your input video. Use --force-cfr --fps 25 (or whatever your real framerate is) to override its guesses.
You'll need about 50 to 100 frames and run two passes:
x264 --bitrate 500 --pass 1 -o output.264 input
x264 --bitrate 500 --pass 2 -o output.264 input
Or perhaps more if you want accurate results with a short clip:
x264 --bitrate 500 --pass 1 -o output.264 input
x264 --bitrate 500 --pass 3 -o output.264 input (--pass 3 is not a typo here!)
x264 --bitrate 500 --pass 3 -o output.264 input
x264 --bitrate 500 --pass 3 -o output.264 input
...
But if three passes isn't accurate enough, fourth isn't going to help. You'll need a longer clip then.
IMO, 8 frames is not enough for any video testing. You need at least a couple seconds at a realistic framerate (10 to 60 fps) for real world video comparisons.
Stream #0: not enough frames to estimate rate; consider increasing probesize
That message comes from libav/FFmpeg which demuxes and decodes your input video. Use --force-cfr --fps 25 (or whatever your real framerate is) to override its guesses.