Extension Key: doc_creating_video_tutorials
Copyright 2000-2002, Michael Perkhofer, Kasper Skårhøj , <michael@perkhofer.at>
This document is published under the Open Content License
available from http://www.opencontent.org/opl.shtml
The content of this document is related to TYPO3
- a GNU/GPL CMS/Framework available from www.typo3.com
TYPO3 is not only documented by text documents. There is also a large archive of "screen shot-videos" with voice over which explains or demonstrates features in TYPO3.
This document describes the methods used to create these videos. The knowledge shared can thus be used by others to create new publicly available videos about TYPO3 so our material for training of users, administrators and developers can grow even more complete.
First I will describe the recommended work flow of creating these videos according to my experiences. Then, you can find sections which describes several other issues which you might be interested in. This includes experiences with other less effective methods and things NOT to do! The work flow to produce the videos is:
Capture the video at high quality (HQ). This can be done using one of the capture tools, mentioned in that document. HQ means lossless video and almost hifi audio. For the video stream, this can be achieved, using the wmv screen capture codec, camtasia codec, camstudio codec, ms-rle. Of course there are other lossless codec, like Huffyuv or Quicktime Animation, but these techniques produce extreme large files, and these are not very easy to handle. For audio we can use WMA @ ~48 kBit/s or mp3 192 kBit/s LAME encoding.
Do the next steps by your own, or send the fresh video to a member of the Typo3 video team (look at typo3.org or search the mailinglist typo3.projects.videos). We will help you, producing the videos and make them public, via typo3.org.
Post processing. You might want to modify video and audio of your footage. Apply a copyright info, cut some part of the film out, paste it somewhere else, etc. You might want to improve audio quality, normalize, dynamic compression, EQ. Tools like Adobe Premiere, Virtual Dub, CoolEdit, Wavelab, Sound Forge are nice to make these modifications. Most of them are commercial, only Virtual Dub (which is really a great tool) is free and open source. Post processing can not be done using the wmv format (or at least there is this free tool from MS, called Windows Movie Maker, it is nice, but wont help us a lot here, due to its limited export possibilities – it is more for weddings movie makers.). So we will need to convert the files to avis and demux them, so we get avis and wavs separated. The result of this step should be kept somewhere as an archive. The typo3.org video team can help you here!
After we have the final footage, we can compress them as a final distribution for the public. The main distribution format is WMV, using the WMA voice codec, including multi language possibilities. For all non Windows Users, we have to offer an alternative format. A mp4 stream + vorbis audio stream, muxed into an ogm or mkv container seems to be an interesting solution, since these files also can be multi language.
OPTIONAL DUBBING: If other languages are dubbed over the video they are recorded as simultaneous translations and using VirtualDub the resulting audio-tracks are inserted in the video-streams instead of the "original" sound track.
vFps | Variable Frames per second. The more the better, but they cost a lot of bandwidth. A PAL movie has 25 fps. Thinking of screen capturings, which is our topic here, some kind of variable fps would be a nice feature, since most of the time, nothing happens on the screen, only from time to time there is some action. Only the WMV Screen Capture Codec can offer this feature. |
Bandwidth | This is measured in kBit/s. Eg. A DVD has ~7000 kBit/s, which is ~875 kByte/s. So as you can see, this is really a lot of data. If we want to offer our videos for download from a website, we have to keep this small as possible. The MS-RLE codec compresses screen capturing to ~130 kBit/s, the WMV Screen Capture Codec reaches the fantastic data rate of only 18 kBit/s. But this will be discussed later. |
Container | Whenever you play a movie on your PC, without even noticing it, you are always playing at least one video stream and one audio stream at the same time. As it is not very practicable to have to handle 2 different files for that, lets say an MP3 audio file and another file containing the video, you pack both into a single file by using a so-called container format file, comparable to a ZIP file. This container and the software coming with it take care of a lot of important functions, like the correct timing of the audio and video playback when the file is played ( opened ). ZIP or RAR could be a perfect container to pack one or more audio/video streams together into one single file for distribution, but WinZIP certainly wouldn't care about the correct timing of the these streams on playback . Known containers are the good old AVI, or the MPEG container ( .mpg , .mpeg ), Quicktime ( .mov ), Realmedia ( .rm ), MP4 ( .mp4 ). We will also discuss the OGM (.ogm) and Matroska (.mkv) containers. |
Codec | The container can hold video and audio streams. The codec is the algorithm, which encoders and compresses the these streams. There are many codecs out there. They are some kind of a plugin, that you can use. Some Video codecs: mpeg-4, WMV 9 Screen Capture Codec, XVID, DIVX, Huffy. Some popular audio codecs are: mp3, PCM, vorbis, speex, WMA Audio Codec Voice |
More to come |
Technology changes and so our solution of distributing videos will have to change. If we want to offer other codecs etc. at a later time, we need to have an archive of high quality material, so that we can produce the best of best afterward. The videos need to be stored in a format, that is lossless and that offers the fps of the original files. The audio needs to be CD quality. So this results in the remaining codecs: WMV Screen, Camstudio and Techsmith Camtasia. For audio mp3s, with min. 128 kBit/s or ogg vorbis files.
After heavy testing, many discussions and long nights of philosophical thinking we came to the conclusion, that the best solution at the time, to develop small and high quality multi language videos is:
WMV 9 Screen Capture Codec + WMA 9 Audio Codec Voice
OGM container using XVID codec for video and vorbis for audio
See the discussion at the end of this document, why we have chosen the MS WMV format.
