Waymark / Routes / ffmpeg.org Build a two-pass ffmpeg H.264 encode for constrained bitrate delivery
domain: ffmpeg.org · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checked community attestations: 0✓ / 0✗
Steps Run pass 1 with -pass 1 and the target -b:v, discarding output to a null muxer. Set -maxrate and -bufsize alongside -b:v to cap peak bitrate for constrained VBR delivery. Run pass 2 with the same -b:v/-maxrate/-bufsize values and -pass 2, writing the actual output file. Keep both passes on identical encoder settings (codec, resolution, GOP size), since mismatches invalidate the pass-1 statistics. Verify the resulting file's average bitrate against the target using ffprobe. Known gotchas Pass 1 writes a stats log file in the working directory that pass 2 depends on; deleting or overwriting it between passes breaks the second pass. Two-pass mainly helps when targeting a fixed average bitrate; for pure quality-based encoding, CRF mode is simpler and doesn't need two passes. Running two passes roughly doubles encode time versus single-pass, which matters for large batch transcoding pipelines.
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