x264 1080p encode, How do they compare up to BluRay source's?

[0028606]

I see a lot of BluRay 1080p movies being re-encode using x264 with a lesser bitrate than the source. My question is how important is the amount of bitrate to the quality of the movie? and how do the the encodes compare to the source?

Are the other setting used such as - No. refs frames, Subme, me_range, Trellis, B-frames, B-adapt etc...
Can these setting make up for the reduction in the bitrate?

[LoRd_MuldeR]

The bitrates used on BD's are way overkill for most sources. At the same time the BD specs force certain restrictions on the encoder which hurt compression efficiency (and hence cost bitrate).

Therefore if you re-encode without the BD restrictions and with a good H.264 encoder, such as x264, you can retain great quality at much lower bitrate than the original BD source was.

Using "slower" encoder settings (more references, more b-frames, slower ME, slower SubME, Trellis, etc.) can squeeze out more quality at the same bitrate - or retain the same quality at a lower bitrate.

But there is a point were using even slower settings won't improve quality any further (in a noticeable way), but only cost additional encoding time. So you must find the best quality/speed trade-off.

However there's no general recommendation, because the best trad-off depends on your personal needs. I'd use x264's "--preset" option as a starting point!

[Dark Shikari]

The bitrates used on BD's are way overkill for most sources. At the same the BD specs force restrictions on the encoder which hurt compression efficiency (and hence cost bitrate).Oh come on, stop exaggerating; the restrictions are pretty minimal except for the keyframe interval.

[nurbs]

The higher the bitrate the closer the reencoded video will be to the original. How much bitrate is needed depends on the complexity of the source material. x264 has the crf mode that is supposed to give the encode as much bitrate as it needs for a constant quality (compared to the original).

The options you mention all change the ratio of quality to bitrate you can get. Slower options will give you a better quality at a certain bitrate, but there is a point of diminishing returns where you have to invest a lot more encoding time for relatively small quality gains. Some of the options like number of refs and b-frames can also influence compatibility to hardware players (resolution, maximum bitrate and other things also have to be taken into account for hardware playback).

Recently a preset and tuning system has been added to x264 which makes it easier if you don't know what options to use. You can look at this thread (http://forum.doom9.org/showthread.php?t=148149) for further information.

[rack04]

Recently a preset and tuning system has been added to x264 which makes it easier if you don't know what options to use. You can look at this thread (http://forum.doom9.org/showthread.php?t=148149) for further information.

The only problem that I've had with the presets is that --tune animation adds --bframes 5. It's my understanding that you can only have --bframes 3 for Blu-ray encodes. This is easily solved by adding --bframes 3 but it could be overlooked.