[Kendall Shaw]

I don’t usually think of problems in terms of being solvable or unsolvable. In this case, when I talk about knowing what I am doing, I don’t mean total awareness. I don’t think that ever happens. I mean knowing what I am doing to some subjectively significant degree.

The choice is not between blindly dealing with each crisis in isolation vs. solving all possible problems. I am seeking a trajectory that is in the problem solving direction.

There is a fundamental difference between the two approaches. In some contexts the difference is obvious, more and more it is less obvious in relation to software because the world largely switched from learning concepts to imitating procedures around the time of y2k.

It’s expected that a doctor will know some signs of a heart attack. The analogy would be knowing some signs of problem video.

It’s not expected that the doctor knows all possible signs of a heart attack. Similarly, it’s not reasonable to expect to know all possible factors that can result in problem video.

If the doctor can only deal with individual cases in isolation, it doesn’t work well. The patient is grasping at his chest, let’s try slapping him on the back. Oh, that didn’t work. Let’s try submerging him in an ice bath, etc. etc. The number of times this results in a dead patient might suggest that this approach is less than optimal. It could lead people to seek general knowledge that can make one prepared to deal with situations that have not yet occurred in a way that is practical.

The switch from concepts to imitation can be seen in technical documentation which used to be reference material but is almost entirely random lists of procedures to imitate in order to perform some task.

For each case in isolation, it requires less effort to follow the procedure than to learn a concept. In other areas outside of the software industry the problems with this idea are too obvious to even be debatable. We teach 4 year old kids the value of learning abstractions.

There are some related aspects to the trend that are good. Extremes in either direction are not practical.

[Kendall Shaw]

Using computers as a measure of caution is a good idea when the cost is low to do so, even if it does not appear to make anything much easier in individual cases. So, something like arrow keys potentially introducing errors in your video that you don’t notice could be something worth taking precautions to avoid.

[Kendall Shaw]

Part of the question in the first post is more or less how does one do benchmarking. Beyond that how do you interpret the results and use the information to point out what you must change to correct the problems.

Different players rendering the video differently would also depend on hd ram etc. A player rendering the video more efficiently than another is a matter of how it performs in relation to those factors.

[Kendall Shaw]

It certainly sounds good. My only exposure to JPEG2000 was when someone was using it to serve giant still images over the web. It’s use would depend on the application of the video. So, it is not a general solution to performance problems, I think.

My question is really about video in general. Even in a scenario in which I could use JPEG2000, I would want to know how to address this problem:

Bob has a computer and will playback a video. Video version 1 and 2 are the same content. Version 1 has an unknown problem.

Video version 1: The JPEG2000 decoder adapts to “low quality” when Bob plays the video.
Video version 2: The JPEG2000 decoder adapts to “medium quality” when Bob plays the video.

I want to know how to figure out what the unknown problem is that leads the decoder to adapt to a lower quality in version 1 vs. version 2.

[Kendall Shaw]

Thanks, that worked.

[Kendall Shaw]

Page up/down move forward and backward along the timeline. In other applications left and right arrow move forward and backward. In AE left and right arrow keys skew the image left and right by one pixel.

So, every time I use photoshop or premiere or virtualdub for example, then come back to AE, I almost always press the arrow key, notice the timeline didn’t move and then try to figure out how many pixels the image was skewed by in order to undo it.

Actually, maybe it means that I have been using the timeline in some atypical mode or something. You are not used to left/right arrow moving the video image left/right by 1 pixel?

[Kendall Shaw]

I want to figure out how to translate factors like those into judging the quality of a video. Video playback can be affected by CPU speed, for example. A corresponding test would be to determine somehow how CPU speed is affecting the playback of some video and what it is about the video that is being affected by the CPU speed.

The opposite is easier, presumably, given some video see if it’s playback is improved by a faster CPU. This approach works to fix the playback of one video for one person, one time.

The point of all this is to have the video playback for other people with unknown computer configurations. When CPU speed affects playback it is a characteristic of the video that allows for CPU speed to affect the playback poorly. That characteristic is what I’m after, for each of however many factors there are.

I have used ffprobe/avprobe before, but aside from finding out what type of video I have, I haven’t known what to do with the information for diagnosing a problem. The same goes for bitrate viewer. The documentation says it helps you to find and get rid of “bad stuff”. The identifying of this “bad stuff” and knowing what to do about it is what I don’t know and what I would have the software for in the first place.

You’ve given me what seems like 2 good ideas at least though, I can use the low level information that I won’t understand coming out of ffprobe on different video files and compare them to see if I can start learning to recognize problems that way. The other is to see what the rationale for hte different mpeg profiles is and to look at the sample test case code for mpeg that’s a public standard.

[Kendall Shaw]

Typically the thread goes off the rails when specifics are brought up. But, the main motivation is that I observe that I automatically seeks a methodical solution to almost any task I am involved with, so it\’s there in my head nagging at me.

One of the nagging thoughts is how to make the process less time consuming when judging whether my after effects compositions are playing back correctly or not.

The most common problem that I deal with is that rendered video plays back in fits and starts. Sometimes uncompressed video plays back smoothly while using youtube 1080p profile mp4 in media encoder the video plays in fits and starts. Sometimes the opposite is true.

The same goes for video bitrate. Sometimes a video file with vastly higher video bitrate plays smoothly for me, while a lower bit rate video file plays in fits and starts. Sometimes the opposite is true.

If one has a faster computer, these become less apparent. But, that is no solution since the audience for the video is people who are not me and who don\’t have my computer.

So far, I have developed superstition about what affects video playback quality. Then when my routine fails I develop a new set of superstitions. I want that to stop and to know what I am doing instead.

I would also like to be able to capture knowledge of what factors affect playback quality into automated tests.

[Kendall Shaw]

A problem is that the target is not a device that a profile was created for, I think. It’s a computer.

Also, I have seen varying performance using the same profile.

But, I hadn’t thought of looking at what those profiles and media encoder profiles do. That probably is a good starting point to look for factors affecting performance.

[Brian Charles] “I don’t think there’s a simple metric since many factors influence video performance, including but not limited to: video dimensions, codec, bit rate, potential hardware bottlenecks: GPU, RAM, bus and disk speed.”

Each of those is a metric. I want to come up with something more specific than each of those and figure out how you would emulate it though. For example, what is average disk speed and how much does it affect video playback performance, in isolation.

I would think that companies that produce a lot of video would have automated tests of some sort as part of QA, instead of relying entirely on people manually checking video to see if they think it looks right.

This is a made up scenario, it’s not the motivation for my question: A different way to think about the factors is if one were asked at a job interview, how would you ensure that videos shipped as video files on CD-ROMs playback consistently for the average consumer? Presumably the applicant would not answer “you can’t” or give some vague answer. Or, the applicant would want to demonstrate to the interviewer that they are aware of general methods to address common problems with video encoding.

[Kendall Shaw]

The option appears to be “NudgeLeft” etc. in the CCompCompCmd section. I did this to disable the shortcuts:

“NudgeLeft” = “()”
“NudgeLeftMore” = “()”
“NudgeRight” = “()”
“NudgeRightMore” = “()”
“NudgeUp” = “()”
“NudgeUpMore” = “()”
“NudgeDown” = “()”
“NudgeDownMore” = “()”

The file is in the preferences area. Edit->Preferences->General->Reveal preferences in explorer (on windoze maybe it says finder on the mac, but it’s so intuitive that you already know).

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