Video Quality Degrading

[Nelson37]

If I have the correct sequence, you played a "bad" file from the external HDD, it was bad, on another laptop, it was good, back to your laptop, it was good. What happened next? THIS IS EXTREMELY IMPORTANT.

You did describe, earlier, files from your laptop which played "bad" on a second PC.

Have ALL file playback tests been made from this same external hard drive?

If some were on USB memory stick, did ANY of the stick-loaded files show a playback change of any kind, in any way?

Do you usually use the same USB port on your laptop?

Have files stored ONLY on the INTERNAL drive showed any changes?

A hard drive can easily corrupt a file. It could corrupt it more than once. It is theoretically possible, but VERY UNLIKELY, that the HD error would "corrupt" the file back into a correct state. Assuming the description of events is correct, with the SAME FILE playing "bad" on laptop 1, "good" on laptop 2, then "good" on laptop 1, then the external hard drive itself is out of the equation. THE USB CONNECTION OF THE HARD DRIVE TO THE PC is now suspect, as it is the only variable known to have changed.

Re-reading you previous posts, you describe burning a DVD and testing playback. This was apparently a simple data DVD copy of the file, with no conversion of any kind, played back on your PC? Also, it played back correctly at least once, on your PC? This same DVD is now "bad"?

Test this disk in the second laptop. If good, that's it, if bad, further testing is necessary.

It is still possible with current information that some element within your laptop is damaging data files and/or disks. It is growing steadily more likely that something specific to your video playback hardware is failing. This failure is actually random, or variable within certain limits, and the random error is being incorrectly associated with a file problem.

Something as simple as tilting the display just slightly can cause laptop displays to appear "degraded", and if any of the video cables, which run right through the hinge on most units, are loose or damaged then just touching the display case can cause a change.

ISOLATE and IDENTIFY. Say it with me.

At this point, I would REPEATEDLY test "old, bad" files, on cold and warm boots, with an occasional "new, good" one. The problem area in the diagnosis is that the files which go "bad" should not STAY that way.

Another issue is that I saw no glaring, easily detectable errors in the sample pics. This raises the possibility that the problem is subjective. One way to help eliminate this, and also possible codec problems, is to start with a DVD rip or similar hi-quality lo-compression file.

What software player are you using, is it always the same one, and have you tried another one as suggested?

[Buu]

If I have the correct sequence, you played a "bad" file from the external HDD, it was bad, on another laptop, it was good, back to your laptop, it was good. What happened next? THIS IS EXTREMELY IMPORTANT.

Almost. At first, I had to re-download the file on the other laptop and open the file in the media player (otherwise it would have played back with the bad quality). After that, I tried the old video which degraded before which then played in the good quality aswell (this was still done on the other laptop). Then I plugged the HDD into my laptop and it displayed good. After that, I plugged the HDD out, plugged it back in and it became bad again.

Have ALL file playback tests been made from this same external hard drive?

If some were on USB memory stick, did ANY of the stick-loaded files show a playback change of any kind, in any way?

Not only the external hard drive, but also an USB memory stick, yes. In fact, each video becomes bad after a while, be it stored on the laptop itself, on an USB memory stick, an external hard drive or even a DVD. It doesn't make a difference.

Do you usually use the same USB port on your laptop?

Yes, I do.

Have files stored ONLY on the INTERNAL drive showed any changes?

Yes, they have.

Re-reading you previous posts, you describe burning a DVD and testing playback. This was apparently a simple data DVD copy of the file, with no conversion of any kind, played back on your PC? Also, it played back correctly at least once, on your PC? This same DVD is now "bad"?

Correct. The files were only burned onto the DVD and played back correctly at least once. And yes, it's apparently "bad" now.

Test this disk in the second laptop. If good, that's it, if bad, further testing is necessary.

Unfortunately, the second laptop doesn't have a DVD drive, so that is out of question. And I have no access to another computer at the moment.

Another issue is that I saw no glaring, easily detectable errors in the sample pics. This raises the possibility that the problem is subjective. One way to help eliminate this, and also possible codec problems, is to start with a DVD rip or similar hi-quality lo-compression file.

Yeah, that was a low-quality video so it's not THAT noticeable (if you compare the eyes, you'll see that the bad one has more "artifacts" or however those are named). Right now I'm still waiting for the one DVD I'm using lately to degrade so I can make a better comparison. Those files apparently are blu-ray rips so it'll be easier to see the changes.

As for the software players, right now I'm using Media Player Classic - Home Cinema but I also viewed the videos in VLC and SMPlayer, each of them showing the same results.

It might also be interesting to note that yesterday I re-downloaded one of the videos that "degraded" before and it had the exact same quality as the degraded one.

[jagabo]

Once again, there's nothing wrong with your files. It's a playback problem.

[Buu]

But why would the videos play back in their bad state on the other laptop aswell? Would the other laptop then have a playback problem too? :S

Edit: Hmm, I just thought of something... Couldn't it be that the videos blur a bit after a while which makes the videos look a bit uglier? I mean, the sharp lines do get blurry after a while, but would that explain why the videos become a bit more "artifact-like" like in a JPG picture?

Just a thought, but I'm not sure if that changes anything on the situation.

[jagabo]

Digital video files cannot blur without the MD5 checksum changing. In fact, they can't change in any way at all without the MD5 checksum changing. Every sector of your hard drive and of a DVD has a CRC code which lets the computer detect if the the data has become corrupt. You would be getting messages from Windows indicating read errors if the drive/disc was corrupt.

[TimA-C]

It's you or the laptop.

[Buu]

Yeah, most likely.

I downloaded a few more episodes of an anime and they already came in a not-so-good quality as they were supposed to. Probably some codec settings are messed up or my laptop's just dicking around.

I'll make a few more tests once I get access to the other laptop but otherwise, there's nothing else left I can really try I assume. I'll give this thread a few more days, maybe there's still someone who got something important to say, otherwise let's consider this situation solved.

Again, thank you all very much for all the help, I really appreciate it.

[jagabo]

Did you try the different output devices in MPCHC?

[Buu]

Of course, I went through each single one but there hardly was any difference. One of them made the video a little bit more blurry but that's it.

[Buu]

I hope it's not too much of an issue if I'm bumping this thread but I wanted to show you the difference I was talking about and finally was able to make a very easily noticeable comparison:

http://i224.photobucket.com/albums/dd303/Buu-Huu/ex1.png < What it looked like before.
http://i224.photobucket.com/albums/dd303/Buu-Huu/ex2.png < What it's after.

This is the kind of degradation I was talking about the whole time. I should point out that I have a new laptop since yesterday and after copying the videos over from an external HDD, the good quality the videos had on my older laptop "degraded" once I played them on this one. Mind you, I re-downloaded the same video but the result stays the same. So basically it's a "download - good quality > format PC - bad quality" situation. Exactly as on my old machine.

I'm at a loss as I'm convinced it's not the computer but I can't find the cause in the videos either. Anyone got any ideas?

By the way, I'm aware that the comparison pics aren't from the same source but it shows exactly what I was referring to with quality loss. Theoretically I could take comparison pics from the same source but I don't want to reinstall my entire OS now. Besides, it would just yield the same result as above so it wouldn't make a difference.

[jagabo]

You just need to adjust your graphics card's video proc amp settings. For example:

[Buu]

That makes sense, yeah, but there's still a problem left: Videos I haven't downloaded before come in good quality with vibrant colors. I made this observation on my old laptop.

Let's say I have three videos. I save them on my external drive (they still keep the good quality) and format my entire machine. Then I copy them over (with the exact same settings I had before the wipe) and they show with lost quality. I download the next episode of the series and it has good quality, just like the older ones before.

Now wouldn't the adjustments in the graphics card settings darken the good quality videos even more than they already were before while the bad quality ones get their vibrant colors back?

I hope that made halfway sense. :S

[Nelson37]

It is NOT POSSIBLE that digital files are degrading on multiple different media.

It IS possible that some software or human effort is making a minor settings change that is affecting this. You seem to be observing an affect that is so minor that time of day and/or the lighting in the room could be the issue.

As for how this happens on different PC's, it is almost certainly the only common factor, the user.

Focus on EXACTLY what changes on playback. Make small, minor changes in PC and setup. Stick with ONE video, go back and forth, you have described a "bad" video which will play "bad, then good, then bad again". The file has not changed four times, something else has. Repeat this sequence until you locate the issue.

[Buu]

You must have misunderstood me because I didn't imply "bad, then good, then bad again" playback in the same video. Once a file is bad, it won't become good again, which is the problem.

Anyways, guess I'll play around a bit with the settings and see what happens.

[jagabo]

The files are not degrading -- period. When there are errors in compressed digital files you do not get slight color/brightness changes. You get very obvious blocky artifacts. Even with uncompressed digital files you get obvious sparkling pixels. You simply have an issue of different players (they can have their own proc amp settings), different output devices (video overlay, vs VMR 7 vs VMR 9, etc.), and different graphics card settings, different graphics card drivers, and files with different levels to start with.

[Buu]

What exactly do you mean with "very obvious blocky artifacts"? It's not only the brightness that changes but also the picture itself becoming more... pixelated. Think of a PNG -> JPG conversion, this is exactly what it is looking like (especially noticeable in darker scenes when everything's "scrubby").

But if you say that they don't degrade just like that, then there's not much to worry about I guess. As I said, I'll keep playing around with the options until I get the image I want.

Thanks for the responses so far!

[jagabo]

What exactly do you mean with "very obvious blocky artifacts"? It's not only the brightness that changes but also the picture itself becoming more... pixelated. Think of a PNG -> JPG conversion

No, it's much worse than that. Exactly what you get will depend on the nature of the error but were talking about something like this:

good:


bad (I manually injected some errors into the video):


You've probably seen errors like this on occasion when watching TV -- when a digital transmission gets screwed up.