Posted: Sat 1 Jan 2005, 2:05 Post subject: Help! Video DEcompression / Conversion problem
I hope I've posted this in the right area - it seemed kind of appropriate!
I've been searching for a solution to this issue for weeks without any success - so if anyone has any insight, I would be incredibly grateful.
I'm about to author a DVD, but the video source which will serve as the main feature (and eventually, parts of the menu's) is in RMVB format. I've rather assumed that it'll require recompression into a DVD compatible format, and so I'm trying to convert it (ideally, uncompress it, I suppose) into something more raw & useable - but I'm having problems.
There are plenty of applications that I've tried which will perform some kind of conversion process - but the only ones that seem to work to any degree, incur unacceptable quality loss (usually in the form of grain).
I've yet to find ANYTHING that will simply allow me to uncompress the video, or convert it using some form of lossless compression like huffyuv.
The most interesting results I've had so far are with the following programs;
TMPGEnc - Opens the RMVB file effortlessly, and performs a slow but reasonable MPEG conversion. However, even with all of the settings at their highest (including bit-rate - at a ludicrous 100,000 kbits per second), noticable grain appears on the output file. I've tried to understand every aspect of the program - be it including only I frames & keeping the aspect ratio's completely unchanged - but nothing seems to prevent the loss of quality.
WinAVI - An odd one this. A discouragingly fast re-encoding process gleaned a .VOB file that was almost identical to the original source video quality aside from periodic visual corruption (for example, it would play perfectly for 7 or 8 seconds, then look like a pizza for a second or two, then play perfectly for another 10 to 12 seconds, then "Bam!" ... more pizza ...). It also resized the video from 640x352 to (what I assume is DVD standard) 720x576, if I remember correctly ...
The absence of grain in the bulk of the WinAVI output made me wonder if the resizing had something to do with it - so I tried resizing the image to the same PAL DVD standard within TMPGEnc as well, but this only increased the quantity of grain in the picture.
Naturally, I expect to lose some quality when I actually author the DVD - but I want to keep this to a minimum. It seemed logical that uncompressing (the RMVB compressed source), followed by recompressing the output using the DVD authoring software's internal codecs/algorithm's would glean the best result - as opposed to converting the RMVB to AVI (or something) and then converting it again to a DVD format ... (which seemed like the wrong way to do things, for the sake of quality).
I have a good 100Gb of available space, so I hope that'll cover any uncompressed video needs (I can probably squeeze more, if necessary).
I hope the above makes some sense to someone - and I'm sure that I've forgotten to mention half a dozen crucial factors, but any assistance would be incredibly useful. I'm completely new to video editing, so I'll hope you'll forgive my ignorence in many respects - but I'm doing my best to do as much as I can on my own!
Thanks for getting back to me - as per usual, your response was quicker than a rabbit in a cat shop.
I gave that application a thorough going over - and had partial (sadly not total) success.
Incredibly, it allowed me to uncompress the source video - but unfortunately, it had two major flaws. First of all, the colour range was reduced so that the blacks became a shade of dark grey (In my very limited knowledge, I'm guessing this might be something to do with the 8-235 colour restriction that's sometimes applied? If this IS what happened, then there was no option to disable it).
The second problem was that the frame-rate was reduced from 25fps to 15fps - I don't quite know why it would have done this (although, again, there didn't appear to be an option to remedy the fact). Do you have any insight as to why that might have happened? Or if you know that all frames would have been preserved, and that recompression into a DVD format could easily make the video 'normal' again? Naturally, the colour loss makes the program inappropriate for use in this instance, but I'm wondering if the frame-rate thing is something I needn't be concerned about if I should stumble upon it elsewhere.
On a side-note, your suggested app pointed me in the direction of numerous others (I think I must have tried close to 20 now. No kidding!). Ultra RM Converter also claimed to transfer RMVB's to full uncompressed files - which is all well & good until you realise that it, too, chucks out some of the colour information (far from lossless).
I really am incredibly grateful to you for taking the time to respond to my initial plea - but, (hate to ask, as I do) - if you can think of anything else that might profer some kind of solution, my depleting supply of head-hair might last that much longer ...
Naturally, in the meantime I shall be trying to find another program that might do the job - although I do seem to be running out of avenues to investigate.
Joined: 04 Feb 2003 Posts: 587 Location: Lisboa, Portugal
Posted: Sun 2 Jan 2005, 18:24 Post subject:
I don't have the (dis)pleasure of working with RM files, so I really don't know which programs work and which don't. Two things:
Are you sure the original file actually does have 25 fps? Remember that 15 fps is not a valid MPEG frame rate, so if you load it into a MPEG compressor, you'll never see it displayed as 15 fps (the closest thing it can do is 30 fps with a dummy B-picture after each frame).
If the source file came from video, its range probably is 16-235 (and not 0-255). The player stretches this to 0-255 during playback, but the original values are in the "video legal" range. In other words, by converting it to a 16-235 AVI, you're not losing any information. It would be compressed into that range when you made the DVD anyway, so just use it as it is and tell TMPGEnc to "output basic YCbCr". Of course, it might be screwing up the colours in some completely different way, but if it's just the 0-255 vs. 16-235 thing, it's not a problem as long as you tell TMPGEnc not to touch it.
Thanks again for your response. I have now resolved the issue (and with luck will never have to mess around with another RM file for the remainder of my days on this planet).
I managed to solve it by getting VirtualDubMod to recognise RM files via AVISynth (there was a guide to doing this at videohelp.com). VirtualDubMod was one of the first applications I tried to use, but it refused to play ball until I'd followed the procedure in the guide - and subsequently I had to install my video codecs in a specific order (which, of course, I failed to take note of - so I hope I don't have to do it again)
Determining the correct fps was a little odd (AVICodec informing me that my RM file was stored at 8456 fps ...), with Media Player Classic giving me the closest approximation of something close to 25fps - but varying slightly every few seconds (variable frame-rate?).
Either way, once I'd told VirtualDubMod / AVISynth that the video was running at 25fps, it let me open it & store it in a much more user-friendly format - and it still had the correct running time, so I seem to have lucked out. I ended up compressing using the Alparysoft v2.0 lossless codec instead of Huffyuv, 'cos Huffyuv refused to work on my machine.
The Alparysoft offering worked a charm - reducing what would have been a 94GB uncompressed video to just over 21GB (still lossless, naturally).
I am (of course) now having a slightly different problem ... but I'll save that for the correct sub-forum ... *lol*
Joined: 04 Feb 2003 Posts: 587 Location: Lisboa, Portugal
Posted: Mon 3 Jan 2005, 3:37 Post subject:
VirtualDubMod was one of the first applications I tried to use, but it refused to play ball until I'd followed the procedure in the guide - and subsequently I had to install my video codecs in a specific order (which, of course, I failed to take note of - so I hope I don't have to do it again) [...] Huffyuv refused to work on my machine.
I wonder if it has anything to do with this (see the last item).
I had actually stumbled upon that FAQ, but your pointing it out reminded me to actually investigate my registry. However, all codecs were listed correctly, with no empty entries - so it would appear to have nothing to do with that.
Although, this said, I haven't tried using Huffyuv since the last round of codec reinstallations ... (I'll let you know if that might have been the cause).
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum