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chipzoller
Newbie
Joined: 15 Feb 2005
Posts: 8
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 Posted: Tue Feb 15, 2005 5:35 am Post subject: Dropped frames? |
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| Has anyone noticed the constant frame dropping that occurs in a converted movie? I've noticed this for a while now with DivxtoDVD. It seems to happen when converting DivX or Xvid AVIs. I also wonder if it might be a combination of the cheap DVD-Rs I'm using and my DVD player. |
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bigly
Junior Member
Joined: 21 Jan 2005
Posts: 53
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| Posted: Tue Feb 15, 2005 7:28 am Post subject: |
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| 1. Do you mean frame dropping as reported in the log window? OR 2. Do you mean you have noticed a visual fault in the output which appears to be 'frame dropping'? If it's 1 then that is due to corrupt/bad data in some frames of your source XviD/DivX - this should only cause momentary glitches in the output if anything. This is nothing to do with your media or player and is to be expected. If it's 2 (e.g. you are experiencing jerkiness/judder) then it could be because your player doesn't like your media BUT it is more likely to be due to the bad frame-rate compensation DivXToDVD uses which I keep raising but no-one else seems to notice!!! |
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JJ
Moderator
Joined: 23 Dec 2004
Posts: 3293
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| Posted: Tue Feb 15, 2005 9:32 am Post subject: |
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| Quote: | | it is more likely to be due to the bad frame-rate compensation DivXToDVD uses which I keep raising but no-one else seems to notice!!! |
Maybe most people don't notice it because their original files are not progressive? I noticed something when I converted two Enterprise episodes, for some reason they were captured as 23.98FPS, (TV-series captured with FILM settings, why, beats me) and I converted them to 25FPS. First episode had no clear problems, but on second sound was out; it looked like bad dubbing. Voices came on right time, but lipsync was not correct. Quite clear indication of frame dropping/duplicating. bigly: send private message or email to developers, don't be too technical. Propose clear points on what to change, as you did on your previous posts. |
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bigly
Junior Member
Joined: 21 Jan 2005
Posts: 53
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| Posted: Tue Feb 15, 2005 11:05 am Post subject: |
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| JJ wrote: | | Maybe most people don't notice it because their original files are not progressive? |
Find this really hard to believe... ...Almost every XviD/DivX which has been 'sourced' from DVD or non-European TV is in progressive format @ 23.97FPS (a.k.a. "Film Mode"). Like you say, even TV shows such as Enterprise are MPEG-4'd like this. The main reason being, XviD/DivX encoding guidance suggests that performing a 'high-quality' de-interlace (pre encode) is much 'safer' than sending out an interlaced package and allowing the 'client end' to worry about de-interlacing or not. (The processing available to a PC de-interlacer during encode is massive in comparison to most client-end 'real-time' de-interlacing). That 'guidance' is also heavily influenced by the main XviD/DivX 'target audience', which is PC (progressive) display. I don't think I have a single XviD/DivX which is in a native interlaced NTSC 30FPS video standard (or native interlaced PAL 25FPS video standard). ["Friends" is about the only 'mainstream' source I know is definitely recorded with a 30FPS interlaced video camera. I haven't got any "Friends" XviD/DivX files but I bet even they would be encoded @ 24FPS progressive. These 'true interlaced' sources (not the interlaced transmission 'source') are the ones where XviD/DivX de-interlaced rips can cause extra artifacts, especially in movement scenes.] I have some which are in a progressive PAL format (such as the BSG files from the UK airing). Again these will have been taken from an interlaced transmission but I think BSG was shot on film so (most) of the actual source will be progressive if it was. Therefore de-interlacing pre-encode returns it to its original 'film' format (albeit speeded up slightly in PAL standard!). [Any editing/special effects done in the video domain (interlaced & cheaper!) can cause extra artifacts during the de-interlacing process similar to de-interlacing a 'true interlaced' source such as "Friends". This is one of the factors which makes some XviD/DivX rips worse than others even with similar encoding parameters.] DivXToDVD using PAL output does a wonderful job with the BSG PAL files because it doesn't do any 'improper' frame-rate compensation. If I forced an NTSC output on these PAL BSG files I would imagine DivXToDVD would do some frame duplication etc. to reach 30FPS. Again, what it probably should do is 'simply' put the progressive frames into an MPEG-2 stream (as it does when PAL output is used) and set the repeat_first_field flag for NTSC 3-2 pulldown in the decoder. If DivXToDVD really wanted to do the whole PAL conversion properly, the main issue is in adjusting the audio stream by the 'incidental' 4% pitch change. (Increase pitch by 4% when encoding a progressive PAL source to NTSC DVD or reduce pitch by 4% when encoding a progressive 24FPS source to PAL DVD.) Even this isn't necessarty though - I'd rather have the audio a semi-tone out on pitch rather than jerky playback.  The only 'complex' conversion is between the 'true native interlaced formats' such as NTSC video to PAL video or vice-versa. Like I say, I doubt many people have XviD/DivX's in either of these source formats though as the interlace is usually removed pre-encode. _______________________________________________ | JJ wrote: | | bigly: send private message or email to developers, don't be too technical. Propose clear points on what to change, as you did on your previous posts. |
Who to? Don't think lapinou likes me!!!  Have you noticed we still don't know whether the 20% increase in file-size fixed anything? |
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chipzoller
Newbie
Joined: 15 Feb 2005
Posts: 8
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| Posted: Tue Feb 15, 2005 1:15 pm Post subject: |
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| No, I should have made this more clear. When I notice frame drops it is upon visual inspection when it's played back on a DVD player. I think also I notice duplicate frames which also causes the choppiness, which is probably the method they're using to compensate for the frame rate. Also, I agree with the previous post about interlaced video. I've never made one that hasn't been de-interlaced from the encode. Most all are progressive from being shot on film. |
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bigly
Junior Member
Joined: 21 Jan 2005
Posts: 53
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| Posted: Tue Feb 15, 2005 3:23 pm Post subject: |
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| chipzoller I think we are 'on the same page'. I was hoping you meant No2 (e.g. problems on DVD playback) as that is exactly what I have noticed all along! You can probably tell I think it is due to the frame duplication, frame rate compensation DivXToDVD needlessly does. I'm just glad other people can see the "chopiness" in the output. (My missus is peed @ me because she wasn't aware of it until I pointed it out and now she sees it all the time!!!) |
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chipzoller
Newbie
Joined: 15 Feb 2005
Posts: 8
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| Posted: Tue Feb 15, 2005 3:30 pm Post subject: |
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| Yes, I've noticed this for a while and thought it might have something to do with my brand of crappy media. I've transcoded other DVDs using these media and haven't noticed similar problems, only when using DivXtoDVD. It seems that their method of frame rate compensation is mostly the duplication of certain frames (keyframes from the source?). And as newer versions come out nothing new in this area seems to have been addressed, so I hope they figure it out soon. And the lack of options involved in doing these conversions probably doesn't help either. In spite of this however, this is still a pretty cool app! |
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