Avoiding and Fixing Common Video Problems

'Jerky video'

I read this complaint a lot and most of the time it is not actually a problem with the video source at all and in fact it's the way the source is being decoded and played back which is the problem.

Take this complaint: "I ripped my footage and encoded it to HuffYUV but the playback is all jerky". It implies that the ripping process is at fault but the reality is that the computer playing back the huffyuv clips is not fast enough to play them back real-time and hence frames are skipped giving the effect of jerky video.

This is also true when using avisynth scripts or when using a codec for your previews that is naturally slow. My advice is to ignore the fact that your source doesn't decode in real-time and simply prerender the source
on the timeline using a fast codec such as an mjpeg codec like picvideo. My editing technique involves putting an avisynth sourced clip on the timeline, selecting the work are and pressing the enter key to do a quick render of it so when I play that section I can see exactly how it looks without jerkiness.

Of course it *could* be the source but the only likely scenario for that is if you have changed the frame rate or decimated the frames in an IVTC process and it has come out looking bad. My only advice here is to look through the way you sourced your video and see if you've done anything silly or if there is another way which is better.

Memory Conflicts when using Avisynth Scripts

This one is nasty, I must admit. Avisynth isn't without its little flaws and one of the problems you will face when editing with avisynth is the memory leaks when using multiple scripts. These memory leaks become more likely the more scripts you use at any one time.

The results of a memory leak can be bad or even disastrous. If a memory leak occurs during exporting, it is more than likely that you will just get some parts of your video exported with a black and red memory error message. However, if a memory leak occurs when an editing program is refreshing the sources your 2 hour footage avs file now looks like a 10 second video file containing an error message. This is especially bad if this change is reflected on the timeline as your edits may well shrink to be one frame long or even none-existent. Premiere does this in a particularly offensive way which means that unless you can load an older saved version of the project then those edits are gone forever. This should be avoided at all costs by doing regular saves with new version names and archived auto-saves etc.

The only possible defence against these memory leaks is in tinkering with the SetMemoryMax preset in Avisynth. This is a value in megabytes that defines the amount of memory that will be allocated to a script when it is loaded. By default this is quite a large value (such as half your computer's free memory) but it can be made to be something specific. In the amvapp there is a file in the avisynth filters folder called setmemorymax.avsi and in it is one line which reads:
SetMemoryMax(64)
If you find you are getting a lot of memory issues then you can reduce this number as you see fit. Too low, however, may stop some avisynth filters from working so be careful. It's a fine art but it can solve most memory issues.

If you are a Premiere user and have installed the Premiere AVS plugin then you can update the setmemorymax number using the Premiere AVS Gui.

Garbage data in HuffYUV exports

Sometimes, some programs get confused by the fact that Huffyuv can deal with both YUY2 and RGB data. When this happens, the program in question starts to mix YUY2 encoding and RGB encoding in the same file. When huffyuv then attempts to decode this, you are presented with a rainbow of horizontal waves. This is obviously not what you were hoping from your lossless codec.

The main way to get around this is to look for an option in your video program to forcibly recompress the footage upon export. This usually does the trick but sometimes....

Bad Premiere Exports

Sometimes Premiere just cannot export something the way you see it on the timeline. This is especially true of new versions of Premiere Pro which seems very selective in which codecs will encode the image correctly. There are other forms of bad encodes which I'm sure exist but almost all of them can be sorted using a very simple idea - get another program to do the encoding.

Sounds great, but how is this achieved? Well, you need to use the DebugMode Frameserver. This excellent tool allows you to serve the timeline to another program, such as virtualdub, which you can use for encoding. This is invaluable when your editing program doesn't like your favourite lossless codec - simply make your frameserver avi file and then open this virtual file in virtualdub and encode using your fave codec.

Pixellated footage where there should not be

In version of Premiere before Premiere Pro there exists a default setting that will make progressive footage look like total ass when it is slowed down. You may be thinking "who would devise such a silly thing?" and the answer is Adobe. In all fairness the reason for this makes some sense if you are using interlaced footage because what is actually happening is that Premiere is trying to deinterlace the footage because if interlaced footage plays back too slow it defies the point of interlacing. It just so happens that Premiere's deinterlacer is the worst the world has ever seen and will make any and all footage look like poop. This is often described as being fuzzy or pixellated.

Avoiding this is easy but remembering to do so is tricky. On your timeline you have to go to your slowed-down clip, right-click, and go to Video Options > Field Options. You then have to DESELECT the option that says "Deinterlace When Speed is Below 100%".

Of course, doing this for every clip in your video is very time consuming. You can, however, do this all in one go! Simply go to your timeline, click ctrl+a to select everything and then go to the Clip menu in the bar at the top (do not right click as this will only select one file). In the Clip menu you will see Video Options > Field Options just like before and can hence deselect this option universally.

Premiere Pro no longer has this deinterlacer. Instead it has a weird an equally nasty frame blender so you may want to disable that in a similar way if it's offending you.

Interlaced footage where there should not be

This one is always a tease. You've spent ages making all your source progressive and as far as you can tell there isn't a single interlaced frame in any of your sources... but wait, when you export there is interlacing everywhere?!?!! What gives?!!

The answer is simple but the reason is subtle. When exporting your project there is likely to be an option that specifies the field order of your video (in Premiere it is to be found in the Keyframe and Rendering section of the export settings) . Your video, being progressive, has no fields so you need to tell the program this. If a field order is specified, what happens is that your editing program will do fades, effects and so on in fields and then interlace them to match that field order, which is why you get an interlaced export. Easy thing to avoid but you have to also remember that project settings and export settings sometimes have to be selected individually so make sure you have this set correctly in both. See the export guide for your program for more info on this.

AbsoluteDestiny - December 2004