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Old 06-21-2011, 04:47 PM
monkeycabra monkeycabra is offline
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Help Question about videos and bitrates

I've bought my X-fi2 a couple of weeks ago, after my Zen Micro died after 6 years of loyal service. It took some getting used to, but I'm really starting to love the thing. The sound quality is just phenomenal, I'm discovering dimensions to songs that I hadn't discovered before.

But that's not what I'm here for. I've put some videos on the player and they keep freezing. I know this is probably due to the bitrate of my videos being too high, but I can't quite figure out what the solution is.
I'm not a total noob, but I don't fully understand what the optimal bitrate is for different video resolutions. I've noticed that the amount of so-called freezing differs for different videos. To clarify, some examples of files:
- 352*624, approx. 1100 kbps
- 480*640, approx. 1000 kbps

I have noticed that for files with lower bitrates the freezing tends to occur less frequent and the same holds for shorter videos (ceteris paribus). But the demo files that were included on the player also have bitrates of 1200 kbps (with a resolution of 272*480), so my conjecture now is that the bitrate in combination with the resolution is the problem.

So, is there someone who can explain to me this whole bitrate thing works (and why it is a problem if it's too high) and how I can solve this?

Many thanks in advance.
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Old 06-22-2011, 02:56 PM
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Brett_val Brett_val is offline
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Well I think you already figured it out yourself; it's a balance between resolution and bitrate. I can't explain (and don't know) exactly why a high resolution or bitrate causes problems other than that the X-Fi2 just can't handle the amount of data being processed. It must have something to do with memory bandwidth, CPU speed, architecture and/or decoding efficiency, but I think at this point all we care about is what does work .

Through trial and error and discussions on this forum and Creative's forum I found that I get the best picture quality by keeping the resolution as high as possible (480p is the absolute max) while compromising the bitrate until it plays fluently. I also tested high bitrates (~1100kbps) while lowering resolution, but to me that didn't look any better than the "high-res" ones.

I think I reached my sweet spot at a resolution of x*300-400 ("x" is there to maintain the aspect ratio!) and a bitrate of 800kbps at max. Something peculiar I found is that videos with a lot of movement in them may need a lower bitrate to play well on this player; for example a stand-up comedy show plays very well at XviD 720x304 778kbps, but for TV-series I even brought it down to 600kbps before I thought it played fluent enough.

As for the two examples you mention, I suggest lowering the bitrate to 750 or so, maybe even lower, and see how it plays. Lowering the resolutions is also an option ofcourse, but like I said I prefer resolution over bitrate.
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Old 06-23-2011, 12:39 AM
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Habhome Habhome is offline
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Quote:
Originally Posted by Brett_val View Post
...
Something peculiar I found is that videos with a lot of movement in them may need a lower bitrate to play well on this player; for example a stand-up comedy show plays very well at XviD 720x304 778kbps, but for TV-series I even brought it down to 600kbps before I thought it played fluent enough.

...
I think that is connected to the encoding and the amount of Key-frames necessary. I don't know if you know how video encoding works, but to save memory you usually keep a few Key-frames, and then only compute the differences between them with some difference-frames, until you need to create a new Key-frame due to a big difference in the image, or reaching a set maximum of difference-frames. So, More movement = more key-frames = requires more computing power to show.

Kinda.
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