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I recently converted a BlueRay movie (Earth --- it's stunning visually...) using Handbrake 0.935 and its default ATV profile.

The movie looks great on the ATV played with XBMC 9.04.1 but around the 2.5 minute mark (the scene with an enormous flock of birds flying above a lake) there is stuttering, both audio and video. I suspect that there may be just too much detail in this scene for the ATV to process.

Which leads to my question: what H.264 encoding parameters can I use for highest quality AND playability with XBMC/ATV? Should the Handbrake ATV profile be playable with XBMC or does this just reflect what is possible with iTunes?

The Handbrake log shows the following encoding info:

[19:06:34] * video track
[19:06:34] + decoder: h264
[19:06:34] + frame rate: same as source (around 23.976 fps)
[19:06:34] + loose anamorphic
[19:06:34] + modulus: 0
[19:06:34] + storage dimensions: 1280 * 720 -> 960 * 544, crop 0/0/0/0
[19:06:34] + pixel aspect ratio: 967 / 960
[19:06:34] + display dimensions: 967 * 544
[19:06:34] + encoder: x264
[19:06:34] + options: cabac=0:ref=2:me=umh:b-adapt=2:weightb=0:trellis=0
[19:06:34] + quality: 20.00 (RF)

Appreciate advice!

Niall

"the scene with an enormous flock of birds flying above a lake", also know as "killa" among teamxbmc. The original is one of the hardest to decode, it crushes my 2.4GHz MacBook with an insane encoding L5.1 with 16 reference frames.

I've yet to hear of any device, including beefy desktops, that can handle the bird scene in that original encode without stuttering. It's just a bad encode. Nobody in their right mind should be using 16 reframes.

I am starting to believe the same, i.e. there is no device that can play that scene, could even a cinema deal with this type of load?

Thanks for your confirmation that the "killa" scene does indeed stress any device.

I finally got an encoding to play without problems two ways:

1. re-encode the first Handbrake encoding using the same Handbrake ATV profile

2. reducing the image size to 796 x 448

Is it worthwhile exploring the rate-limiting capabilities of X264? I have seen references to the rate limitations of the ATV. What are recommended limits? I am trying with vbv-maxrate=4900:vbv-maxbuf=2700 -- are these reasonable?

Niall

niallgal Wrote:Thanks for your confirmation that the "killa" scene does indeed stress any device.

I finally got an encoding to play without problems two ways:

1. re-encode the first Handbrake encoding using the same Handbrake ATV profile

2. reducing the image size to 796 x 448

Is it worthwhile exploring the rate-limiting capabilities of X264? I have seen references to the rate limitations of the ATV. What are recommended limits? I am trying with vbv-maxrate=4900:vbv-maxbuf=2700 -- are these reasonable?

Niall

bit rate is only part of the equation.

1) encoding profile (L3.1, L4.1, L5.1)
2) cabac and number of reference frames
3) image size
4) encoding bit-rate
5) audio encoding params matter too if you are on the edge.