On sobota, 15 marca 2008, Justin Ruggles wrote: > I agree that this would be a good task, and also that it won't be as > easy as the others. The qualification task is so that we have some > example of your coding abilities and dedication to the task. Having > another sample of your code won't really help us. We already have that. > > :) I would like to see your dedication to last year's task by helping > > to get it ready-for and into FFmpeg SVN. > > I have just been very busy lately with other stuff. If I can get help > with getting these things done, and then a final patch made which makes > it into SVN, that would go a long way. I do want to be clear that this > would not guarantee a spot, but it would qualify you to be considered on > the merits of your proposal and all of the other factors we use to > decide which projects get chosen. > > Here is my current plan of action regarding AC3 and E-AC3, which is > subject to change if needed. > > 1. Get the fast, simple AC3 downmixing working based on Rich's > suggestion of doing the short-block downmixing after the IMDCT but > before the overlap/add/window. I want to do this first because it will > likely change the structure of the decoder a bit, which will be easier > before E-AC3 is integrated. Right now I'm getting artifacts. My plan > is to analyze a single frame, in depth, to find out where the problem lies. > > 2. Right now AC3 is suffering from a major stability problem. There are > many coded values which affect how many bits are read, and the bitstream > reader does not have any built-in protection from reading past the input > buffer. So malformed or damaged streams can (and do) cause memory > access problems (detected by valgrind) and/or segfaults. I have several > ideas for solutions to this, but I need time to test each one to see > which is the fastest. > > 3. Go through the list of invalid bitstream conditions in the specs and > add as many of those checks as possible. Some may not be needed if they > significantly decrease decoding speed and do not affect stability. I > have already started on this...it just needs to be tested and applied. > > 4. Do the same condition checks for E-AC3 as well, but we don't have a > nicely prepared list to work from.
Ok. Unfortunately, most of the conditions from AC3 hasn't much in common with E-AC3, but I'll try to think of some correctness tests of the stream. > 5. Update the E-AC3 decoder to include all the changes since last update > and any subsequent changes. I should do it before or after those 3 points which I was given? > 6. There are a couple of samples which seem to be 7.1-channel. It would > be nice to get this working before SVN inclusion. I haven't seen 7.1 files. Where can I find them? > 7. Error conclealment. Simple error concealment is fairly trivial. For > more robust detection and concealment, Michael made some great > suggestions for guidelines. It would require some reworking of the AC3 > parser. Can you give me some more explanations on this topic, because I think I don't understand what do you mean properly > 8. Prepare a final patch and go through the ffmpeg-devel review process. > > So that's about it. :) If anyone feels I should skip any of these steps > or change the priority, I am open to suggestions. > > That said, I think a good SoC qualification task would be to work on #4 > to #7 while I concentrate on #1 to #3. Then once that's all ready, do > #8. I will, of course, help with all of this and would make sure to > prioritize this over my other on-going projects. Ok, so I treat #4 to #7 as a qualification task, I'll try to do them as soon as I have some free time:) -- Bartlomiej Wolowiec _______________________________________________ FFmpeg-soc mailing list [email protected] https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-soc
