Question about video codecs/containers and playback differences.

[superboyac]

I have questions about video player formats, codecs, containers, etc. that never gets properly answered because people get carried away with the technical jargon of it.  My question is, what are the differences and what causes the differences?  Please keep this novice friendly, don't go crazy about the technical details.

For example, I know if someone asks, "What is better; avi or mpg?"  The answer they will get is a long thing about how avi is a container and many formats fit in it.  Ok, i get that.  Whatever.

My real question is how come I get different playback experiences with the different formats?  Is it just me or what?  In light of all this, I'll give little nuggets of information, based on my experiences in the past:

--wmv files normally have more issues for me compared to avi or mpg.  Seeking in a player is usually more quirky.  I think it's more sluggish also.

--avi files seem to generally play back the best for me.  Never any problems.  Seeking is quick and pleasant.  Sometimes there are sync issues with audio.

--mpg files also seem to generally be trouble free.  Not as common as avi, but stable.

--mp4 are usually ok, but problems come up often.  I blame this largely on it being an apple format and how most pc's will not want to play those out of the box.  So you have to get quicktime.  but i don't want quicktime, so I get Quicktime Alternative, or a player like KMPlayer which plays everything.

but does anyone experience this also, where you have different experiences with different extensions (regardless of what combo of containers/codecs you use)?  I do.  Even now, if I see a wmv file, i'm always a little hesitant.  If I see an avi and wmv of the same thing available, I'll get the avi.  These are my impressions, however uninformed.

[Renegade]

A lot depends on your codecs and media player. Not all are equal, and there are alternatives for almost everything out there. e.g. Fraunhofer vs. LAME vs. Blade, etc.

Overall, there's no simple answer.

If you're on Windows, then you're ahead of the game. Macs just don't have any support for a lot of codecs. Same with Linux. Not a poke at the OS, but a weakness in how many developers are attracted to the platforms and willing to do codecs.

On Windows, buffering is generally fairly short, which gives you smooth video at the risk of decreased stability.

For AVI, it's highly dependent on the codecs used. Again, no simple answer.

DiVX and XViD are both very good. They're usually in AVI files.

Matroska files can be very heavy sometimes. (MKV)

Basically, I think MPG and AVI are safest, but I tend towards AVI there as well.

Size (resolution) is also a big factor. Full HD is much more taxing on your CPU. Normal TV resolution is easier to play.

Not sure if that helps any.

[superboyac]

No, that's helpful.  I'm just looking for a discussion here, not an in depth analysis.  Yes, i also find mkv files to be very heavy, as you say.  But I also notice that people who use mkv files are making more high quality videos, like full HD or just very big multi gigabyte files.  For example, the only mkv files I have rips of music dvd's that are uncompressed, I think.  I use that program makemkv.  The quality is great, but I can't play those files on my old computer.

So what is it about wmv files that make them more annoying than avi?

[Renegade]

WMV and WMA are actually extremely good. The problem is WMP. WMP is a platform, and not really a player so much. It's better to fire up Visual Studio, drop in the WMP control, and get that working. You don't have the WMP heaviness then. WMP, Real/RealPlayer/QuickTime are all platforms. My favorite there is RealPlayer, then WMP running very close behind. QT is just garbage to use.

If you work with WMV, try using the Microsoft Windows Media Encoder. It's pretty good. Keep in mind that it's really a platform, and so you have a bit of overhead for a few platformish things there.

I'm not sure, but WMV seems to be a bit heavier to decode than some others. Perhaps someone that's more up on things can comment. I've not done a lot of work with it in a few years.

[superboyac]

I'm not sure, but WMV seems to be a bit heavier to decode than some others. Perhaps someone that's more up on things can comment. I've not done a lot of work with it in a few years.

Yes, it is heavier.  And I bet I know why.  Copyright copyright copyright.  wmv has that copyright stuff built in.  The ability to only allow playback a certain number of times and stuff.  It's all built into the codec, so it makes it run slower, harder to move the seek bar around...just generally makes it a worse experience so that copyright features can be added.

[MilesAhead]

For mkv playback, the new VLC player has improved somewhat. It now has support for PGS subs, the kind that are in BluRay movies.  Also this surprised me. It can now display xsubs in .divx files. The kind you add with AviAddXSubs.  Before that the only player that could display them afaik was DivxPlayer, which is not smooth.

If you don't have to worry about subtitles the best playback on the PC I've found for .mkv is Splash Lite.  Even the new VLC will stutter and pause when you move the slider.  Splash goes right to the spot in the movie.  Also it supports video hw acceleration depending on your video card.

The biggest weakness in stand-alone .avi/.divx players is they are limited to standard DVD resolution.  You couldn't play HD avi or divx files.  But the new Divx Plus they are coming out with is all .mkv now.  The .mkv is going to be the new wave.  Looks like they will support HD .mkv and .avi/.divx and probably .mp4 on the new Divx Plus players.

Set top box seems the most versatile. I have WD HDTV player for USB.  The main hassle for me is subtitle support.  But it plays a variety of HD format files.. .avi .mkv .divx .mp4 and they look good.  Eventually they should support PGS and a lot more subtitle formats.  Unfortunately I have the 1st generation of the player so there will be no more firmware updates afaik. If you get the "live" player with the networking support you'll probably have the most options and they will keep updating it.  Gen1 is hosed.  I have to live with it as it is. It does have its good points though. It supports USB 2.0 docking stations without doing anything. Just leave the dock plugged in and swap hard drives to change the movies.

[superboyac]

The biggest weakness in stand-alone .avi/.divx players is they are limited to standard DVD resolution.  You couldn't play HD avi or divx files.  But the new Divx Plus they are coming out with is all .mkv now.  The .mkv is going to be the new wave.  Looks like they will support HD .mkv and .avi/.divx and probably .mp4 on the new Divx Plus players.

i didn't know that!  I didn't realize avi./divx had a resolution limit.  Is that why all the HD videos I've seen are wmv or mkv?  Must be.  Yes, Splash Lite is a good little player.  If they can beef up the customizeability like a KMPlayer, it could easily be my player of choice.  it definitely deals with HD files  nicely.  Sometimes when I have an HD file (usually wmv or mp4) I always have to try a few players before it work smoothly.  KMPlayer doesn't always handle them well.  Splash usually does a god job, but even that sometimes doesn't work.  Light Alloy also does well occasionally, sometimes when no other player works.  But Light Alloy doesn't have built in decoders, it just uses your system configuration.  And I have a special decoder installed for HD stuff, I forget the name right now.
But I think the trend I see is this: any format that is proprietary or built in with copyright features is going to give you more trouble than the more general/open use formats like avi/divx/xvid/mpg.  And that is what is annoying.

I am beginning to like mkv a lot because it can do more than the other formats, such as subtitle enabling/disabling, built in chapters, etc.  That's really nice to have it all in one file rather than using VOB files or something like that.  I'm also looking forward to Googles open format that I've heard a little about.

I generally don't like wmv, wma, realplayer, even mp4 sometimes (but mp4 has been ok for me so far).  But I'm always a little suspicious of any of the formats that are proprietary to apple, microsoft, etc.  because you always know they won't do it the best way possible because one of their primary concerns will be copyright protection.

[JavaJones]

The biggest weakness in stand-alone .avi/.divx players is they are limited to standard DVD resolution.

I've bolded a key point there. It's the players, specifically the *hardware* set-top players, that can't play HD in AVI/DIVX containers/formats. The AVI container and various video codecs that can be contained within it can handle HD just fine. You can even put h.264 into an AVI container. It's not an "officially supported" option but most decent players (e.g. KMPlayer, GOM, Splayer, MPC, etc.) handle it just fine.

Anyway to answer your question, it sounds like there a few general points which may help you understand.

There are several elements that go into determining your video/audio playback experience with any given content.

The container (AVI, MKV, etc.) mostly influences what kind of data can be embedded in the file and how easily it is parsed/accessed. So an older container format (e.g. AVI) won't have as much flexibility as far as embedded or multiple subtitles or multiple audio tracks or menus, and will have generally have less supported flexibility in video/audio codec combinations. The container can affect your playback experience to be sure, particularly where it comes to streaming, but mostly it's the codecs and content within it that will do this. That being said, containers do generally specify the way in which the data may be stored, accessed, and "interleaved" (audio/video sync). So this can affect (and cause problems) in particular with both seeking (the granularity allowed for chunk access) and for audio/video sync (AVI for example doesn't handle A/V sync with certain video/audio codec combinations).
See here for more:
http://en.wikipedia.org/wiki/Container_format_%28digital%29#Multimedia_container_formats

The codecs used can influence both audio and video quality, playback performance on given hardware, and especially seeking, startup, and streaming performance. Some codecs are optimized for small chunks of data without much interdependency, which makes them potentially good for streaming and seeking, but may decrease their encoding efficiency for example. h.264 strikes a great balance for video though, generally speaking. AAC likewise for audio. Both allow good streaming (in the right container formats), and pretty much the best currently available quality at a given compression ratio. WMV (actually this is usually a reference to an ASF container format, though the file extension may deceive you) as a container, and the WMV codecs that may be inside it, are generally less friendly to random seeking, and are also often times heavier on system resources when decoding (if not hardware accelerated), hence your experience and resulting preference in media files. I have the same preference and tend to avoid WMV files unless they're the only thing available.

Remember that a codec is really both an encoding method/process and a decoding method/process. The "method" is a software system of some kind. So if you have a particularly good or bad encoder, it can affect the end result, and likewise if you have a particularly good or bad decoder, it can affect the result/experience. On the encoding end for example, you can have encoders that support more advanced features, or you can use special encoding methods like multi-pass which give you improved quality for a given bit rate, or better compression. On the decoding side you need a decoder that supports all the features of the encoder, and one that operates efficiently with low CPU use, perhaps even one that's accelerated by a GPU in your system, or that is multithreaded for a multi-core CPU. This is why there is a market for high-performance format decoders like CoreAVC. See here for more:
http://en.wikipedia.org/wiki/Codec

Finally, the system you play things back on obviously has an effect, and this is not just the hardware, but also the software environment as I said above. You may get a really well compressed h.264+AAC file in an MKV container but be unable to play it back well because you don't have a speedy decoder, or your decoder isn't multithreaded, GPU-accelerated, etc. But the hardware is of course a huge influence. For most playback needs a fast single core CPU serves you best. RAM is generally not too important, though some very large files and particular players or playback methods may require surprisingly large amounts of memory. Generally the chunk size of a video/container will determine this though, and if properly done no video file, even upwards of 25GB (Blu-ray files) should require more than 100MB of memory for your player.

Anyway I think that gives you something to chew on.

- Oshyan

[MilesAhead]

It's only the stand-alone player that has the limitation on .avi playback resolution.  I have Philips upscaling .divx Ultra certified DVD players.  They can play back both NTSC and PAL format.  For that reason, they must have limited the resolution to 720x576.  So if you have a 720P .avi you are out of luck.  I was in the ridiculous position of downsizing .avi files so that I could then put them in my upscaling player.

That's one of the reasons I bought WD set top box. It can play 720P and 1080P .avi files.  The main problem with .divx on it, it doesn't know anything about xsubs.  So even though I have embedded xsubs added with AviAddXSubs, I have to include an .srt file if I want subs.  You can have the .srt as a stream in the video file for .mkv but it can be set to automatically load external .srt files so it's just easier to include them that way.  Plus the more streams you have in the file the greater the chances for going out of sync.  Biggest pain of WD player is often if you have .srt subs you can't even use Stop without risking the subs going out of sync. All you can use is Pause.
That, and processing speed is why I'm hoping jdobbs will update BD Rebuilder so I can just burn in the subs and not have to worry about timing and all the rest of it. Once they are burned in they can't go out of sync.

The nicest part of my setup is I have USB 3.0 docks on my PCs and a USB 2.0 dock connected to the WD player.  Although I don't have network support it's not so bad as I can just pull out a HD from one of the USB 3.0 docks and insert it into the USB 2.0 dock next to the set top box.  Pretty convenient that way. Plus by using BD Rebuilder or Quick AVI Creator I can fit a lot more movies on a HD.

In fact I just ordered a WD Caviar Black 1 TB 6 Gb/sec HD to store more flicks. This latest generation of WD drives are nice!! I have a 640 GB version of the same drive. I can read from it with USB 3.0 @138 MB/sec.  This TB drive has the same spec.

[superboyac]

javaj, great explanation.  I'm going to have to bookmark that.  i knew a lot of it already, but the way you explained is just what I'm looking for.  Not overly technical, and very clear.  Thank you.