Comment 12 for bug 349011

Hi all:

I'm the creator of DeVeDe. I'll copy the question and answer 8 from the FAQ:

"#8 I adjust the bitrate to use the 100%, but the final size is smaller.

Unfortunately is impossible to accurately predict the disk's final size, because you specify a bitrate, but Mencoder can decide to use an smaller value in certain parts if it can compress it more without quality loss (like in very static scenes). That means that the final size can be smaller than the estimation made by DeVeDe, but never bigger."

Currently, DeVeDe estimates the final size with the formula:

        FinalSize = (Video_bitrate + Audio_bitrate) * lenght_in_seconds

Unfortunately, Mencoder sometimes uses less bitrate than the specified. I suspect that this happens mainly in already compressed sources (like ones in DivX or Xvid), because mencoder can keep the final quality without loosing more quality.

I asked Mencoder creators for another way of stimating the final size, but they answered that there is no alternative: the current method is the only one. You can't predict where Mencoder will be able to use less bits per second without already compressing the videos.

Sorry.