ABR and x264 HQ-Insane, HQ-Slowest, HQ-Slower vs. LAME --alt-preset insane, extreme

[venky]

Hi All,

I have been a little confused regarding the use of the x264 encoding profiles with ABR encoding (fixed filesize). I know that the different profiles turn on and off different aspects of the encoder. But given that with ABR you are fixing the size of the output file how much do these different optimizations matter? Do people in general see video quality decrease in the following order:

HQ-Insane > HQ-Slowest > HS-Slower ...

I am trying to understand using an analogy from MP3 encoding. Lame uses a number of presets e.g. Insane, extereme, standard etc. Now when I use these presets in LAME I get files of different sizes and different quality (generally accepted), with insane giving the largest files and maximum quality, extreme smaller file sizes and lesser quality and standard the smallest of the files and the lowest quality of the three.

In the case of MP3 encoding I can understand the relationship between the different presets and the resultant files. But in x264 ABR (fixed filesize) encoding the relationship between the encoding profiles and filesize is less clear.

Can somebody help me understand the relationship between video quality and encoding profile?

Thanks,
Venky.

[akupenguin]

If you want an analogy, lame's most similar options are -q / -f / -h.

[venky]

Hi akupenguin,

My only acquaintance with lame is using it with the presets, so I am not very clear on what the other options mean. When you use the switch -q/-f/-h do you also have to supply a bitrate? (You don't with the presets)

[check]

There is no analogy using only lame presets. The idea of x264 profiles is that they increase the coding efficiency. This means you either get a higher quality stream in the same amount of space, or the same quality stream in a lower amount of space (or some combination of both).

[ggf31416]

Venky, your analogy is not good. The presets in LAME are one way to select the target quality or the target bitrate:
--preset medium = VBR V5 ~140 Kbps
--preset standard = VBR V2 ~ 200 Kbps
--preset extreme = VBR V0 ~ 250 Kbps
--preset insane = CBR 320kbps

They are the equivalent of the -q setting in Nero AAC Encoder or in OggEnc. The closest equivalent in megui to the LAME presets is the Bitrate/Quantizer (CQ)/Quality (CRF).

A better analogy is the compression level of an archiver. A higher setting means an smaller archive but a slower compression and a lower setting means a larger archiver but faster compression.
However (unless you select lossless mode) x264 is lossy. At the same quality (CQ or CRF) the higher setting (e.g. HQ-Insane) gives a smaller file and the lower (e.g. HQ-Fast) an larger file. At the same bitrate a higher setting provides better quality and a lower setting provides worse quality.