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Thread: How to compress your movies | Forums

  1. #1
    It's a question that has been asked many times before, and will be asked many times to come – "How do I compress my movie?"

    Whatever codec you use, and there are many, the most important figure is the bitrate. The higher the bitrate, the more bits you get and the higher the quality. More bits also mean a larger filesize. So you have to decide on a bitrate that keeps the filesize down, but the quality up.

    If your movie is to be downloaded over the Internet, you will want to keep the size as low as possible. A good bitrate for short downloadable movies is 1.5Mbps (1.5 megabits per second).

    There are three main codecs that are currently the best to use:

    * Windows Movie Maker encodes movies with the Windows Media Video (WMV) codec and is the simplest to use. It also has the advantage that anyone with a Windows PC will almost certainly be able to watch your video without having to install any other codecs. It's main disadvantages are that it is fairly limited in its options and also a lot of non-Microsoft applications will not recognise it.

    * In my opinion, the best codec to use is the propriety DivX or its competitor, the free XviD. At the time of writing, I consider DivX to offer slightly better quality.

    * The third most popular codec is the H264 codec used in QuickTime .mov files. I know nothing about this as I'm a PC, not a Mac! You'll have to buy it, by the way.
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  2. #2
    Windows Media Video (WMV)

    WMV is the simplest to use. Edit your movie in Windows Movie Maker and when you are ready to render it you will come to the ˜Movie Settings' window. Click on ˜Show More Choices', then ˜Other Settings', and you will get the full range of encoding options. There are not a lot of choices but a good one to use is ˜Video for local playback (1.5 Mbps PAL)'. This will give decent quality and the filesize will be about 11MB per minute.



    For this to give the best results, your input video clips should be at least 720x405 (for 16:9 widescreen) or 720x576 (for 4:3 normal screen).

    The framerate should be 25 frames per second. Note that 25fps is quoted as PAL standard which is actually irrelevant. PAL and NTSC are TV formats and are of no consequence for watching video on computers. NTSC settings will be at 30fps which is a waste of bits and leads to larger filesize. The ideal framerate for digital movies is 24fps but Windows Movie Maker does not have this option, so PAL is the closest.

    If you want to save a higher quality version of your movie for storing on your hard disk, then use the highest possible setting. ˜Video for local playback (2.1 Mbps PAL)' will give better quality and a filesize of around 16MB per minute.

    I tested these settings with a 4 second uncompressed clip. Uncompressed, the filesize was 82,514KB. Compressed at 1.5Mbps reduced the filesize to 756KB. That is over a 100 times smaller!
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  3. #3
    DivX (or Xvid)

    Many video editing programmes like Sony Vegas and Premiere Pro can compress the final movie with DivX. However, this process often leads to problems. It is far better to render your movie uncompressed and then do the DivX compression using VirtualDub.

    If the filesize from your editor is far too big, then you could compress it with the HuffyUV codec. This is a lossless codec. It will only reduce the filesize by about 4 times, but it will do so with absolutely no loss in quality. I do this all the time with Sony Vegas without any problems at all.

    Download and install DivX from HERE.

    Load your movie in VirtualDub. The first thing to do is set up the audio compression. The best audio codec to use is the LAME ACM MP3 Codec. This gives better quality than the MP3 codec that comes with windows so download and install it from HERE (installation instructions are also on that site).

    Click on ˜Audio', then ˜Full processing mode'.

    Click again on ˜Audio', then ˜Compression'.



    Select ˜Lame MP3' then choose an audio format. 44,100Hz, 128 kbps, ABR, Stereo gives good quality. Increase that to 192kbps if you want really good audio quality. Press OK to close the window.

    Now click on ˜Video', then ˜Compression'.



    Select 'DivX' and click ˜Configure' and the DivX properties window will appear.



    There are many settings that you can change, but for a beginner it is best to start with the default settings and only make a few changes. To make sure nothing important has been changed, click on ˜Restore defaults'

    You can now enter a specific bitrate and compress your movie. However, you can make a significant improvement to the quality if you use multiple encoding passes.



    Select ˜Multipass, 1st pass' and type in the bitrate you want. For a resolution of 720x404 and 24fps, then try a bitrate of 1500kbps. Press OK.

    Select ˜File' and ˜Save'. Give your movie a name and save it. This first pass does not actually produce a watchable movie, it is only creating a file with video information that will be used in the next pass.

    Once complete, do not close VirtualDub. To carry out the second pass, select ˜Video', then ˜Compression', select DivX again and press ˜Configure'. The only thing you change here is to select ˜Multipass, Nth pass'. Press OK twice.



    Select ˜File' and ˜Save' and do not change the name. Press ˜Save' and you will be warned that the file already exists. Click ˜Yes' to replace it. This replacing process takes the video information in the first pass to produce a better quality movie in the final ˜Nth' pass.



    Experiment to get the right bitrate. Some movies need a higher bitrate to get acceptable quality, some can get by with less. Movies with a lot of movement like in action dogfights need higher bitrates. Movies with little movement like a static view of an actor talking do not need such a high bitrate.

    You now have a better quality video than the wmv version, it is not a propriety format so can be played in many more players (including some modern DVD players connected to a TV) and the filesize is very close to the wmv version.

    You will, however, have to make sure your viewers install the DivX codec, or Xvid. Movies compressed with DivX or Xvid can be played back with either of them installed.

    The instructions for Xvid are almost the same for encoding with DivX if you prefer to use Xvid.

    I hope this all helps!
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  4. #4
    hello Joe;
    well done; this wraps the whole process up very neatly;
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  5. #5
    Senior Member Doolittle81's Avatar
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    Excellent job.

    This thread definitely needs to be Stickied as soon as possible.
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  6. #6
    Fantabulous!
    Very easy to understand when explained by an experienced person.

    After spending too long making films, I need some of this DivX compression magic on my waistline too.....
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  7. #7
    Senior Member 310th Falcon's Avatar
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    S! Joe

    Excellent job again mate!

    It needed to done long ago for our young and upcoming film makers.

    Sticky please... any Mods in the mix??


    Best Regards
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  8. #8
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    hi all,

    i might want to add a link which covers most possibilities and offers pretty detailed guides for encoding:
    mpeg-4 encoding

    in general, for the final encoding process, 'gordian-knot' is a fine cover-all solution, which includes an interface to chose codec, file-size, cropping and other features... and the download also includes additional tools (like mp3-encoding for sound).
    all is free and explained for individual codec on the link above.
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  9. #9
    Many video editing programmes like Sony Vegas and Premiere Pro can compress the final movie with DivX. However, this process often leads to problems. It is far better to render your movie uncompressed and then do the DivX compression using VirtualDub.
    Hello Joe; Recently I compress directly from Vegas with the DivX codec, multipass and experienced no problems. By eliminating the Virtual Dub loop you save a lot of time and space.

    Question: It seems that there is a quality loss of sound if the Audio uncompressed option is selected? Do you find this as well?

    Again great posting of you this one; what software you use for the tutorial? freeware?

    keep well
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  10. #10
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    hi biltongbru,

    on the advantages of 'virtualdub':
    since commercial non-linear editing programs mostly try to find a niche in the market to be able to compete, they develop each their own rendering engines to excel over other brands.
    most noticeable has this happened with 'adobe premiere' with the change from v5.5 to v6 or 'pro' (who will ever understand, that versions change so fast meanwhile, that they need to introduce new product-lines every 2 years meanwhile). with that change ('premiere' had been just a 'supporting'-application for 'after effects' before), 'premiere' lost many sympathy in the progressive market (like full-digital processing as done with game-screening), but gained a huge advantage over 'avid' in dv-production. the downside was, that there was less to no interest for 'mpeg4'-support, the program was optimised for dv-source editing and exporting to dv again.
    this said, one has to consider, that most other editing software has it's own optimised renderer as well and even if 'vegas' is much more friendly towards 'mpeg4'-export, the total process of rendering and then exporting and encoding needs a continuous use of temporary fragments. which in most cases interferes with the codecs capability for motion-detection and optimising bandwidth - and is also more time-consuming.
    some products give the option to prerender the timeline, which makes much sense, but that way the same huge file is created as when exporting as such.

    by using 'virtualdub' for encoding, the additional advantage is to specufy the desired colourspace and also to have the probably smallest and best-working application doing the 'avi'-job, that there is.


    for the audio-artifacts:
    audio-processing is a problem for most editing software. quite often the audio is resampled internally or being changed to frame-count, while processing the video-tracks. this happens often, when the project (or the video-interpretation on import) is set to some standard-format. although it is needed in cases of live-footage to assure synchronisation, it is undesirable, when working with captured video.
    also in that regard, it is a good idea to use the editing-software only for cutting and synching the timeline, but furtheron export audio and video separately and then mux it again, when encoding it in 'virtualdub'.


    for the huge, intermediate file:
    there is a franeserver included in 'virtualdub', which makes use of most default filters. it can be set up to pull out audio/video from the editing software (as client) and hand it over to 'virtualdub' as proxy. it works flawless, but setup confuses me always a bit, so i never really used it often. however, from what i remember, the frameserver does a full 1st pass on the prerender, before having 'virtualdub' finishing the 2nd pass (for 'divx'/'xvid'). that way one avoids the fragmentation during analysis and also the intermediate file before encoding.
    though, i didn't really have a closer look at the results for comparison - so it might be just a suggestion for experiment.
    however, using the frameserver and 'virtualdub' for encoding is still faster than compressing with 'vegas' or 'premiere'.
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