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From Stefano Mazzocchi <stef...@apache.org>
Subject Finished Video Processing
Date Wed, 15 Oct 2003 13:01:38 GMT
All videos has been grabbed, cut, subtitled, exported, encoded and 
uploaded.

Go to http://www.apache.org/mirrors/, select your favorite one and then 
go to

/cocoon/events/gt2003/videos/

if it's not there, wait for a few hours.

PLEASE, do not use the main www.apache.org web site!!

The video is AVI with a video stream encoded using Mpeg4 (DivX) and an 
audio stream encoded using Mpeg 2 Layer 3 (Mp3). The stream bitrate is 
around 164Kbps, so you could watch it realtime even with moderate 
bandwidth.

                                       - o -

Some info on the processing.

Hardware used:

  - Sony DCR-TVR30E (shooting, storing)
  - TiBook 1Ghz 512Mb 60Gb (processing)

Software used:

  - MacosX 1.2.8 (Jaguar)
  - Apple iMovie (cutting, processing, subtitling, exporting)
  - divx5.1/mencoder/ffmpeg (encoding)
     - my talk was encoded in divx5.1 beta
     - the rest with mencoder
     - matthew/gianugo/david's talk and the panel was encoded with ffmpeg

Note: some were encoded with 320/200 size while some 320/256, I 
apologize for this but I didn't know PAL doesn't have 4:3 aspect ratio 
:-/ [you learn something new every day]

The reason for the various encoders used is that both divx5 and 
mencoder are buggy.

divx5 is currently alpha state on mac, unusable, crashes and when it 
doesn't crash it creates horrible visual artifacts (like diagonal green 
lines on the video stream!!!) I found this out encoding Sylvain's talk 
and there was no way to get back, so I needed an alternative.

Mencoder (found inside MPlayer) is pretty good, much faster than divx5 
and seems even better quality (for what i can tell). Unfortunately, it 
doesn't work as a quicktime plugin so I had to export the video from 
iMovie.

In order to make it faster, I exported as a full quality DV stream. 
Exporting DV from DV clips is fast because it doesn't need a additional 
codec pass, but it requires an additional 10Gb for the exported stream. 
So, for an hour of presentation you need at least 20Gb! Luckily I had 
that space on my HD.

I ended up doing exporting/encoding in parallel since iMovie is faster 
to export the DV stream (doesn't have to reprocess it!) than it is 
mencoder/ffmpeg to encode it.

I was also able to upload at the same time, so, after having grabbed 
the clips from the video camera (which happens at 1:1, so takes an hour)

  clips -> iMovie -> file -> encoder -> file -> scp -> remote file

all at the same time. pretty cool when it's 3AM and you had enough ;-)

That parallel processing takes about 3/4 hours per hour of video. 1 
hour for clip grabbing, 2/3 hours for export/encode.

The problem with Mencoder is that it has a bug reading some DV streams: 
it believes they are encrypted. ffmpeg has no problem on the same 
streams (and no decrypt libraries built in) so I guess it's a bug in 
mencoder. (note that mencoder uses the same ffmpeg libraries for 
divx/mp3 encoding! so quality is the same!)

Now, the best of both worlds would be an ffmpeg plugin for quicktime. 
that would *rock* (and save me 10gb of disk every time!) but the 
ability to do parallel export/encoding doesn't make it much different 
if you have enough disk space (it's just a lot slower because of 
simultaneous disk access)

Well, took me forever, but now I'm satisfied of the results :-)

Enjoy.

--
Stefano.


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