I'm having some trouble rendering my movies. I upload one video per day to YouTube. Previous videos were fine, but yesterday, after I uploaded video number 77, I noticed the audio was out of sync. I tried rendering and uploading again, same result. My local video on .webm format does not have that problem, audio syncs fine.

I was suggested to use MPEG-4 or H.264. My .webm movie is just 13 Mb, but when I export on MPEG-4, no matter which bitrate I choose, the result is 60.4 Mb, which I consider a waste of space since the 13 Mb looks perfect already (it's screen casting stuff).

Why is the bitrate ignored?

I also tried H.264. The rendering crashes almost immediately.
And MPEG-2 gets stuck at 99%.

I'm not being very lucky...

BTW: I'm using Ubuntu 11.04, Kdenlive 0.8, ffmpeg version git-2011-10-25-1ca1336, x264 core:119 r2106 07efeb4

Workaround: after exporting the large mp4 movie, I can reduce the 60 Mb file down to 11 Mb with:

ffmpeg -i movie.mp4 small.mp4

I wish I could do without this extra step though. The quality is worse than with a webm file of the same size.

Using MP4 instead of WEBM doesn't work out. This is the MP4 version with good audio sync but very poor resolution. The text in the video can not be read, looks blurry:

http://www.youtube.com/watch?v=r6PG56eZ7so

and this is the WEBM version with bad audio sync, but much higher image quality. The text can be easily read in the video:

http://www.youtube.com/watch?v=BUnGtMUxGjY

BTW: the poor image quality is something caused by YouTube. Locally both MP4 and WEBM look almost perfect, but somehow YouTube reduces the MP4 quality much more than the WEBM quality.

Any tips are welcome. Right now I'm stuck...

I feel a bit silly talking to myself in this thread :)

I wanted to share my progress on this. I just updated Kdenlive to 0.8.2 (awesome list of bug fixes!). I also downloaded the latest versions of ffmpeg, x264 and libvpx using GIT and compiled them myself.

Now when I export on WEBM format the result is twice as big as it used to be, and the bit rate setting does not seem to have any effect when rendering.

If I run "ffmpeg -i result.webm" on a movie I rendered yesterday I get 208 kb/s. Same movie rendered today, same settings, 411 kb/s.

"I feel a bit silly talking to myself in this thread :)"

You might get more response if you actually gave details of what settings your are using. Bitrate alone doesn't give much information. Are you using an encoding profile that ships with kdenlive, or did you create your own? If so, what are the settings?

You sound like you've been using Quicktime too much. Bitrate is actually quite a poor metric of encoding quality. There are quite a few settings that have drastic effects on quality and compression ratio besides just a bitrate setting. Especially when dealing with h264.

Thank you for your reply. I'm sorry if I don't give enough information, but I'm quite new at this and don't know yet what's important and what's not. I tried Quicktime about 10 years ago. I haven't created any encoding profiles. I use the standard ones.

1) What I'm surprised about is that exporting a movie with bit rate 10000 gives a file with the same size as a movie with a bit rate of 2000. Shouldn't the bit rate be directly related to the size of the resulting movie? They also don't look any different in quality.

2) I'm also surprised because after updating Kdenlive, ffmpeg and x264 the same movie that used to render to a 13 Mb file three days ago, now results in a 28 Mb file. No settings changed.

This is briefly my problem:
* I create a new video every day.
* I export it using WEBM and upload to YouTube
* Since the last two episodes, the audio is off sync on YouTube, fine locally.
* I wrote to YouTube. They told me WEBM is not supported, even in their own web site it's listed as option #1.
* I tried to explore other formats, but the quality once in YouTube is terrible, so much that the text in my video is unreadable. Locally it looks fine. It looks like YouTube reduces the quality of MP4 videos, not so with WEBM. While testing rendering formats, I noticed file sizes are not affected by bit rate; MPEG rendering got stuck at 99%; H.264 rendering crashes.

And the solution:
* Drop YouTube and switch to blip.tv. They accept WEBM. The same exact video that was off-sync in YouTube looks fine in blip.tv. They also publish updates to Twitter and Facebook when I upload a new episode, they push the video to dozens of other video hosting sites, you get your own blip.tv/url, and you can customize the looks of your site. For now it looks good.

Well x264 is not involved in creating WEBM. It would probably be due to changes made to libvpx, which is the library ffmpeg uses to encode WEBM in the preset. There may also be changes in the options for ffmpeg with WEBM that have not been updated in Kdenlive's WEBM profile. And there's always the possibility of bugs.

But it looks like you found a working solution.

You might want to check out something like Arista or Transmageddon to see if those work better for what your are trying to do.