vc2


SMPTE VC-2 (previously BBC Dirac Pro). This codec was primarily aimed at professional broadcasting but since it supports yuv420, yuv422 and yuv444 at 8 (limited range or full range), 10 or 12 bits, this makes it suitable for other tasks which require low overhead and low compression (like screen recording).

'b'

Sets target video bitrate. Usually that's around 1:6 of the uncompressed video bitrate (e.g. for 1920x1080 50fps yuv422p10 that's around 400Mbps). Higher values (close to the uncompressed bitrate) turn on lossless compression mode.

'field_order'

Enables field coding when set (e.g. to tt - top field first) for interlaced inputs. Should increase compression with interlaced content as it splits the fields and encodes each separately.

'wavelet_depth'

Sets the total amount of wavelet transforms to apply, between 1 and 5 (default). Lower values reduce compression and quality. Less capable decoders may not be able to handle values of 'wavelet_depth' over 3.

'wavelet_type'

Sets the transform type. Currently only 5_3 (LeGall) and 9_7 (Deslauriers-Dubuc) are implemented, with 9_7 being the one with better compression and thus is the default.

'slice_width'
'slice_height'

Sets the slice size for each slice. Larger values result in better compression. For compatibility with other more limited decoders use 'slice_width' of 32 and 'slice_height' of 8.

'tolerance'

Sets the undershoot tolerance of the rate control system in percent. This is to prevent an expensive search from being run.

'qm'

Sets the quantization matrix preset to use by default or when 'wavelet_depth' is set to 5

  • - default Uses the default quantization matrix from the specifications, extended with values for the fifth level. This provides a good balance between keeping detail and omitting artifacts.
  • - flat Use a completely zeroed out quantization matrix. This increases PSNR but might reduce perception. Use in bogus benchmarks.
  • - color Reduces detail but attempts to preserve color at extremely low bitrates.