dumb question about x264 lossless

[deadrats]

ok, this may sound like a truly stupid question, but for the life of me i can't figure out why it behave as it does. in another thread manamo recommended i try XviD4PSP because it has the best auto interlace detector available and i must say the whole app is actually really nicely done. it also allows one to use a variety of filters and one of them is the one that seems to be everyone's darling at the moment, QTGMC.

as jagabo had stated in another thread, QTGMC is painfully slow, even with the fastest settings (not "ultrafast" which uses yadif) so i started experimenting with various x264 encoding options to try and maximize speed. i decided to try x264 lossless and here is where the results confuse me.

i fed into Xvid4PSP a ~32 minute vob with 4mb/s mpeg-2 and 256kb/s ac3. i cropped the black borders, used BlackmanResize and set the output to 640x480. i then chose QTGMC with the "very fast" setting and i chose x264 lossless.

the output was huge, it produce a file with a bit rate of 40mb/s for video!!!

why should this be? to me lossless means sans loss, if you're starting with a 4 mb/s mpeg-2 and you're using what is presumed by it's advocates to be the best h264 encoder currently available, then shouldn't a lossless setting result in a maximum of the same bit rate as the input?

or does x264 lossless behave like more traditional lossless codecs, such as huffy, i.e. it results in a less compressed output than x264 in regular use? or does x264 lossless only use I frames?

i just don't understand why x264 lossless results in such drastically increased file sizes.

[poisondeathray]

why should this be? to me lossless means sans loss, if you're starting with a 4 mb/s mpeg-2 and you're using what is presumed by it's advocates to be the best h264 encoder currently available, then shouldn't a lossless setting result in a maximum of the same bit rate as the input?

or does x264 lossless behave like more traditional lossless codecs, such as huffy, i.e. it results in a less compressed output than x264 in regular use?

Yes, it's lossless like huffyuv, lagarith etc...

Lossless codecs are lossless compared to the decoded output (ie. uncompressed output) . So compared to the uncompressed output, filesize will be smaller, usually at least half or less

e.g
compressed video=> decoded => uncompressed video => lossless compression

or does x264 lossless only use I frames?

x264 can be configured to use I-frame only or long GOP

[manono]

manamo recommended i try XviD4PSP because it has the best auto interlace detector available... .

I think XviD4PSP is a pretty decent program too, if for no other reasons than the ones you mentioned - a variety of filters available, and a variety of output formats available. And it also accepts AviSynth script input. But to set the record straight, as far as I know XviD4PSP doesn't analyze a video for interlacing and choose what to do based on what it finds. If you're referring to my comment here:

https://forum.videohelp.com/threads/351431-how-to-deinterlace-in-most-appropriate-way?p...GK#post2204369

it's AutoGK that can analyze a video for hard and soft pulldown and pure interlaced video. It stumbles on the tough stuff though - displaced fields and field-blending. Nothing beats using your eyes for determining what you have and how to deal with it.

[deadrats]

manamo recommended i try XviD4PSP because it has the best auto interlace detector available... .

I think XviD4PSP is a pretty decent program too, if for no other reasons than the ones you mentioned - a variety of filters available, and a variety of output formats available. And it also accepts AviSynth script input. But to set the record straight, as far as I know XviD4PSP doesn't analyze a video for interlacing and choose what to do based on what it finds. If you're referring to my comment here:

https://forum.videohelp.com/threads/351431-how-to-deinterlace-in-most-appropriate-way?p...GK#post2204369

it's AutoGK that can analyze a video for hard and soft pulldown and pure interlaced video. It stumbles on the tough stuff though - displaced fields and field-blending. Nothing beats using your eyes for determining what you have and how to deal with it.

that was the thread! i was going crazy trying to find it, funny you recommend AutoGK, but my memory played tricks on me and it became Xvid4PSP in my mind, lol.

but, Xvid4PSP does analyze an input video (you can even set the percentage of the input file you want analyzed, to be safe i'm using 100%) and it will tell you what type of interlacing was used but seems to default to QTGMC for de-interlacing.

i have to say so far i'm pretty impressed, Xvid4PSP does an admirable job with those tough greek comedies i mentioned in the other thread, i do have one question though, what the hell is DVC QTGMC? it does a really nice job denoising and preserving detail, but my God, it's slow, i want to pull out all my hair that i don't have since i shave my head!!!

i'm also in the process of trying to do a half-assed "port" of QTGMC from avisythn to vapoursynth in the hopes that it will better take advantage of multiple cores.

@poisondeathray: thanks, from some reason i combined x264 + lossless and came up with something other than what in retrospect was an obvious answer.

[manono]

...but, Xvid4PSP does analyze an input video (you can even set the percentage of the input file you want analyzed, to be safe i'm using 100%) and it will tell you what type of interlacing was used...

Oh, it does? Then thanks for the correction. I just don't trust any of the auto-analyzers (even AutoGK's, although for rookies it's pretty good). It's just not that hard to figure out for yourself what's going on. A combination of DGIndex (if the source is some sort of MPEG), looking at frames, and separating out the fields, can tell you just about all you'll need to know.