I've been encoding ABR 1-pass at 256kbs based on handbrake's iPod low-res profile and been more or less happy. 2-pass took too long, and I didn't even think about constant quality (nor know about CRF, or that handbrake's 'quality' means RF). After researching this stuff heavily, it looks like I was wrong to use ABR in the first place, as variable file sizes is OK (to a point). I want the variance to center on a value, and avoid even brief excursions outside the 'bitrate limited' specifications of the iPod 5G. (Though I now use a 6G(3G) nano)


So, trying to come up with an optimal preset for 320x176 (generally, 240 sometimes, and to hell with movies that start off at 320x128, they going to lose some side pixels). Picking a quality is personal, but I am aiming for something that comes close to 250-300kbps on a reference video I'm using (Veronica Mars S2 ep6, FWIW). I do not care if it hits average 512 on Armageddon, but don't want much above that. Seems no way to allow a instantaneous spike limit of 2500, but with an average limit of 512. If 2-pass CRF had a meaning, I guess something like that would be it. (But it doesn't, isn't supported, and handbrake doesn't allow manual setting of 1st pass option string)

There's a line in the activity log that says "muxer track 0, xxxxx bytes, xxx kbps" but the kbps is never the actual average bitrate of the resulting video as far as I can tell. So, since this episode codes to 107MB at 256 ABR, I'm shooting for 100-125MB and trying different quality settings to get there. Then I'll just use that quality, and accept whatever filesizes I get off other sources.

So...
Here are settings, with my questions after each. Comments MUCH appreciated.
I've done a TON of research, but at this point need to ask some of you guys for help.
---------------------------------------------------------------------------------------------
cabac=0 {have to do these 3 for iPod}
bframes=0
8x8dct=0
---
keyint=300 {rule of thumb. But, why does activity log always show these set to 250 and 25 even after 300,30 specified}?
keyint_min=30
---
vbv_maxrate=2500 {According to earlier post, these are the real limits for even a 5G iPod? max 768 or 1500 too conservative?}
vbv_bufsize=2000
---
ref=2 {max for the 5G, 3 not worth it imho anyway and does add both enc and dec overhead}
mixed_ref=1 {why not, tho shouldn't make much diff with only 2 ref. Little more decode overhead, but if you care, refs=1}
---
me=umh
subme=6
me_range=16 {raise this a bit?}
no-fast-pskip=1 {why not? low enc overhead, no decode overhead}
chroma_me=1 {this is not in the handbrake file, should it be? or is it a default of the encoder now?}

The webpage that specified chroma also said to use "+cmp -flags +loop -T" and maybe a few others.
What are those and does the advice still apply or is it outdated?
http://rob.opendot.cl/index.php/useful- ... ing-guide/
---------------------------------------------------------------------------------------------


And here are settings I frequently have seen on iPod-ish profiles that seem to be ill-advised:
---
trellis=0 {I have heard this is very bad for any 1-pass, and questionable for 2-pass ABR. yes?}
decimate=1 {I hear detrimental to any ABR/CBR, and only maybe should be off if using trellis=1 on 2-pass ABR}
deblock=1:0:0 {3 numbers for deblock? same as "yes" with 0,0 offsets. This is default, why specify?}
analyse=0x1:0x131 {how do you interpret these hex numbers? I just say "all". Should I use none for higher quality or some limited set like p8x8,i4x4}
---


I haven't seen any of these, any idea what they are?
---
mbaff=0
deadzone=21,11
chroma_qp_offset=0 {default I think}
nr=0 {noise reduction?}
---



Not sure why or if I should specify any of these. Are any CBR/ABR specific?
---
brdo=0 {irrelevant if you have 0 b-frames?}
threads=auto {any reason to set to anything else?}
ip_ratio=1.40 {aren't these 5 all the defaults anyway?}
qpmin=10
qpmax=51
qpstep=4
scenecut=40
---

Are these CBR/ABR only?
---
rc=cbr
bitrate=9000
ratetol=1.0
rceq='blurCplx^(1-qComp)'
qcomp=0.60
---