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Old 28th November 2006, 03:39   #1  |  Link
Beak
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Good bitrate for viewing on 30G Ipod?

Hello.I am purchasing an Ipod video for my son this Christmas.

I just used AutoMKV (thanks to anyone who had a hand in this!) to encode Scarface. I used the PD-Ipod profile.

It is 2 hours 44 minutes.I selected the 700Mb option and used an audio bitrate of 128, leaving a video bitrate of 460 average.It looks fantastic,even double sized.

Is this bitrate reasonable for the tiny screen it will be shown on,or can I go lower and still look OK?

I am not so concerned about file size as battery life. I don't think my son will be using TV Out but you never know.

Any thoughts would be greatly appreciated.
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Old 28th November 2006, 03:42   #2  |  Link
Sharktooth
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the bitrate selection depends on the final filesize you want (hence the duration), the resolution and the movie compressibility.
basically, if the encode looks good then it's ok...
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Old 28th November 2006, 03:49   #3  |  Link
Beak
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Thanks.

I was wondering about the AGC level and battery life for the 460 bitrate.

Would I get significant battery savings with a lesser bitrate? I was reading about AGC levels with MeGui and I want the files to use as little processing power as possible and still look OK on the little screen.
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Old 28th November 2006, 04:09   #4  |  Link
Sharktooth
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yes, the more the bitrate the lower will be the battery life but you can also disable deblocking and cabac and keep a higher bitrate (switching off cabac will lower the compression by ~10%... so it will require a 10% higher bitrate to obtain the same quality).
Those two options are cpu cycles hungry, so disabling them will help the battery life a lot. Keep in mind quality will be lower.
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Old 28th November 2006, 05:21   #5  |  Link
Beak
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I have located cabac and deblock in the advanced editing field.Deblock reads true and cabac reds false.

What should they read and how are they changed?

Will the ipod automatically adjust the AGC or will this need to be changed as well?

I could be out to lunch on this AGC thing but my understanding is that this tells the ipod processor at which speed it must run at.Does AutoMKV set this automatically?

Thanks for your help again......
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Old 28th November 2006, 05:42   #6  |  Link
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I am saying AGC when what I mean is AVC.
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Old 28th November 2006, 07:24   #7  |  Link
DarkZell666
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Just to clean things up for you :

AVC (aka H.264) is the codec standard used for encoding the videos

x264 is one of the AVC codecs available (which many tools out there use, including AutoMKV ). Note that x264 is the only free H.264 encoder available to date.

The ipod profile you used, contains a set of options for x264, which are required for the produced file to be ipod-compatible.
So all the "ideal" settings for ipod are already configured for you.

Quote:
my understanding is that this tells the ipod processor at which speed it must run at.
This isn't even possible

All options in x264 (and any codec for that matter), provide a tradeoff between quality and filesize, and/or between quality and decoding speed. This is probably what you were talking about, and decoding speed rather refers to "the amount of cpu required for the video to run smoothly". For example, some options will require only 60% of the ipod's cpu power to have a smooth video, and other options will need the full 100%. This is what the ipod profile is partly designed to avoid. (the principle is the same wether we're dealing with an ipod or not but it's just to make it simple ).

Beware that on an ipod, the video has got to have a rather small resolution, like 320x200 (or 400x300, dunno precisely). And I don't have a clue wether AutoMKV automatically sets this or not , so you might have to set it manually after loading the ipod profile.

I hope i've been clear enough and that you'll be able to get this done before christmas
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Old 28th November 2006, 10:53   #8  |  Link
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I recommend using either MeGUI or StaxRip.

I use a resolution of 640 pixels wide (Native DVD is 720). Then for the target bitrate I use 1000 Kbps for the video, and 100 Kbps for the audio. This means a DVD movie comes to about 800 - 900 MB. Bigger for longer films.

The actual command line I use is:
Quote:
C:\Program Files\megui\tools\x264\x264.exe --pass 2 --bitrate 1000 --stats ".stats" --level 3 --no-cabac --subme 6 --analyse none --qpmin 16 --vbv-maxrate 1500 --me umh --merange 12 --threads 2 --thread-input --progress --no-psnr --output "" ""
Change --threads 2 to --threads 1 if you don't have a 2 CPU / Dual Core CPU.
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Old 28th November 2006, 16:57   #9  |  Link
HowlerX
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Just a few things:

It's been my understanding that the iPod can't handle files encoded with CABAC. I never actually tested this, but it's what I gathered from reading these forums. So it's a good bet to have CABAC turned off when encoding video for your iPod.

simonhowson's suggestion about encoding video to a width of 640 pixels is only applicable if you intend to watch the video on a TV from your iPod. If you intend to just watch video on the iPod screen I don't recommend anything higher than 320 pixels wide. When the iPod downscales any video to fit the screen it introduces color-banding and image quality suffers.

Of course, simonhowson could be encoding video to a 640x resolution in anticipation of the long-rumored next-gen Video iPod which might (should!) have a higher resolution screen. I should also mention that getting H.264 videos with a width of 640 requires a modified version of MP4Box since iTunes will NOT download it to your iPod otherwise.

Whatever your preference, I hope my suggestions helped. Bye!
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Old 28th November 2006, 19:11   #10  |  Link
ilovejedd
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The latest iPod release (5.5G) already supports 640x480 resolution. From Apple's website:
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Video formats supported: H.264 video, up to 1.5 Mbps, 640 by 480 pixels, 30 frames per sec., Low-Complexity version of the H.264 Baseline Profile with AAC-LC audio up to 160 Kbps, 48 kHz, stereo audio in .m4v, .mp4, and .mov file formats; H.264 video, up to 768 Kbps, 320 by 240 pixels, 30 frames per sec., Baseline Profile up to Level 1.3 with AAC-LC audio up to 160 Kbps, 48 kHz, stereo audio in .m4v, .mp4, and .mov file formats; MPEG-4 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per sec., Simple Profile with AAC-LC audio up to 160 Kbps, 48 kHz, stereo audio in .m4v, .mp4, and .mov file formats
So if your son is unlikely to watch videos on anything other than his iPod or maybe a CRT TV (CRTs are very forgiving), then stick to 320x240.

On my PSP which has a slightly bigger screen than an iPod, video encoded at 320x240 @ AVC 384kbps still looked fine.
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Old 29th November 2006, 01:05   #11  |  Link
Beak
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Thank you all. I am sticking to around 600Kbps including audio at 128.

I have scareface playing perfectly in quicktime, but itunes rejects it as an unsupported file type.I have switched the container type in AutoMKV to mp4 along with the ipod profile.
Resolution is 320 x __.

Is mp4 container incorrect? I tried to recode with MKV container and the encode failed with an AutoMKV shutdown.
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Old 29th November 2006, 03:24   #12  |  Link
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No... sadly it's itunes that's incorrect...
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Old 29th November 2006, 03:38   #13  |  Link
Beak
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Quote:
Originally Posted by Sharktooth View Post
No... sadly it's itunes that's incorrect...
What can be done? How do I use AutoMKV to get a DVD on to this ipod?

It works perfectly in quicktime!
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