[FFmpeg-user] Setting bitrate on qtrle codec (QuickTime Animation)

Bob Maple bobm-ffmpeg at burner.com
Wed May 21 02:27:09 CEST 2014

On 5/19/2014 3:31 PM, Eduardo Grana wrote:

> Hello!
> I'm having trouble setting the bitrate when encoding with qtrle,
> it seems to be always encoding the same way.

You can't really control the bitrate like other codecs, and I believe
ffmpeg always works in 'lossless' mode - it doesn't have the weird
streaky-artifact mode like Quicktime Pro does when you bring the quality
slider down below 100%.

You can however sometimes lower the effective bitrate by playing with
the keyframe distance with -g which can really help with things like
screen captures, where you have a lot of solid colored areas (that
benefit from RLE in the first place) and not large portions of the
screen changing from frame to frame (like mouse movement.)

If you compress random or otherwise complicated motion video with qtrle,
using "-g 1" or "-g 100" more than likely won't have much of an affect
on the finished file size, but the latter will just compress slower and
the resulting file will be slower/harder to seek like any other coded
with I-frames spaced very far apart.

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