Can video files be corrupted during download/playback?

vbimport

#1

Hello, I posted a similar question earlier on Yahoo! Answers and got ridiculous answers … don’t know if I was misunderstood or something, but let me ask this a different way:

The web page talks about the reasons why you might encounter dropped frames when recording/encoding/converting video on your computer … I’m basically focusing on the issue of system resources (CPU/RAM).

I know even from personal experience that performing too many tasks WHILE you are encoding or capturing video can cause dropped frames (framerate reduction) in the finished product (as also stated in the link above).

HOWEVER … what I was asking was if the SAME thing could happen when you are DOWNLOADING video files, NOT recording or converting them.

For instance, if I am downloading a video file (or files) from YouTube or some other website/server … do I need to worry about what else I might be doing at the time (such as browsing the internet)? This doesn’t seem to make sense to me.

Assuming that your HDD, internet connection, and power supply are all FINE, how could using system resources possibly affect the PLAYBACK of a DOWNLOADED video file?

I mean, are you telling me that the video might lose frames (or otherwise become “corrupted” in some way) simply because I was doing something else while downloading at the same time? This sounds preposterous to me, and from personal experience, I’ve never encountered anything like this.

I’ve always been able to perform other tasks on the computer while my downloads ran in the background. That to me is normal. As I stated before, this is assuming that, this is assuming that there are NO HDD, connection, or power issues whatsoever. This isn’t about that. I’m concerned solely with the affect that system resources allocation has on the downloaded video.

Just for argument’s sake … even if that DID happen … that because I was multi-tasking during the download, not even CPU/RAM was available and frames in the video were lost … most video formats wouldn’t even PLAY if that was the case, would they? In addition, if frames were lost, then that would be reflected in a DECREASE in the SIZE of the video file, would it not? I’ve never encountered unplayable video files or file sizes that didn’t match the source due to this.

It’s ridiculous to think that a downloaded video is going to lose frames or become “corrupt” unless you absolutely dedicate all of your CPU/RAM during the download. We’re not talking about the possibility of faulty hard drives or dropped internet connections here … we’re talking about NORMAL CIRCUMSTANCES.

You’re telling me that if you’re downloading files via torrent totaling 10 GB … you’re not gonna do anything else on your computer for what … half a week? In addition, you’d be uploading data at the same time, so already that’s extra system resources being used.

What about streaming videos online? By definition, when you stream a video, you are simultaneously watching and downloading the video at the SAME TIME. And that could use quite a bit of resources, especially if the video is in HD.
I’ve never encountered corrupted videos while watching HD videos on YouTube.

In addition, what about when you play a video file in WMP or VLC? By that logic, each time you access/play the video file, you have a chance of “corrupting” it in some way.

Say you have a favorite video file on your computer that you watch regulary (for whatever reason) … you’re gonna tell me that the more times you play it using a media player … the more likely it will become corrupted (such as lose frames or something)? We’re not talking about a VHS tape here … which loses a tiny bit of quality each time it runs in the VCR.

These are DIGITAL video files. You’re downloading the complete file. As long as you have no power, connection, or HDD issues, then you should either download the COMPLETE file perfectly as it is … or not at all. I refuse to believe that because I was ALSO browing the internet during the time of the download that the video is now going to be missing frames … seems absurd.

When you are converting/recording video, you are creating/writing the data … when you are downloading a file or playing it back, you are ONLY accessing it, not changing it in any way. There is NO FILE MODIFICATION, is there? Therefore no change in quality (including frames).

Say you have an old computer with a bad video card. You play a video file on it, and the playback results in major screen tearing and dropped frames. My question is … will that playback affect the video FILE itself afterwards? In other words, if you copy the video file over to a better computer with a good video card, then will the file play in its original quality?

Or will the file be “damaged” after having been played on the “bad computer” that resulted in the “bad” playback?
In other words, does the screen tearing and dropped frames “carry over” … or is there zero modification to the file during playback?

I guess what I’m asking is, can playing a video file on an outdated computer with a bad video card (that results in choppy playback and tearing) “damage” the file? Or is the file still exactly the same as it was before the playback? My understanding is that there is no MODIFICATION of a video file during download or playback … only during encoding/converting?


#2

You won’t damage a file by playing it.

It is, however, possible to get a corrupted file when you download it. Look up the term packet loss. This is generally due to problems in your internet connection, rather than processes running on your computer, though some download managers and firewalls have been known to interfere with download completion. A corrupt download doesn’t often work, and if it is compressed, like a zip file or rar file, it won’t open properly.


#3

[QUOTE=Kerry56;2623745]You won’t damage a file by playing it.

It is, however, possible to get a corrupted file when you download it. Look up the term packet loss. This is generally due to problems in your internet connection, rather than processes running on your computer, though some download managers and firewalls have been known to interfere with download completion. A corrupt download doesn’t often work, and if it is compressed, like a zip file or rar file, it won’t open properly.[/QUOTE]

Thanks, this is what I figured.Even if a video file were to be corrupted, then it would either a) have entire seconds missing or b) depending on the file type, not even play/load at all.It would be quite unlikely that you would dropped frames or a reduction in framerate as a result.That’d be like if someone were blindfolded and randomly stabbed a knife into the air … and it ended up hitting you right in the eyeball (unlikely).However, this was not consistent with the ridiculous answers I was getting on Yahoo! Answers. Too many “sky-is-falling” OCD types answering questions there.


#4

If the file header is corrupted then its a bit work to get it done.
You may can restore the header using vlc or Virtualdub.

Structure issues in the files can be also fixed up to a point, but cannot be repaired without loss. Re-downloading is the only solution in such a case.