Im delighted to hear you are planning a knowledgebase, because these encoding issues get complex and theres plenty to say on the subject. I reckon on average I spend at least a few hours every week talking about various encoding issues, usually in response to specific questions.
Ive never tried to summarize everything thats been said about mpeg4 encoding here, its not a small task, but if theres anything of use in psat messages of mine, you are welcome to reuse anything Ive written. In repsonse to specific questions youve asked or others have subsequently raised: Yes quicktime is just a container format. Most of the quicktime .mov files used today are also mpeg 4. The advantages of not wrapping mpeg4 up as a mov are so that it can be playted without conversion by a wider range of software and hardware. The downsides include some servers not setup to handle mpeg4 mimetype, some users computers not setup to have an app associated with .mp4 files, and .mp4 files currently dont support metadata, wheras .movs have metadata capabilities. Also the fact that 3ivx only seems to want to export its mpeg4 to .mov files (at least on the mac anyways). For a time many believed that .mp4 files also lacked the fast start option, which is an important thing, but I believe it turned out not to be true, though I forget how the confusion started in the first place, or what settings are needed. So anyway if you are already experienced with encoding to mpeg4 .movs, most of the 'science' behind the settings is identical. Bitrate, framerate, keyframe, audio settings and considerations should be the same. (unless you are targetting specific hardware devices that can play mpeg4, but only up to certain resolutions, bitrates, or profiles. Eg some devices may only support mpeg4 basic rather than improved, but until the hardware mp4 video market becomes clearer I wouldnt start worrying about this too much yet) What may vary is where the options are and exactly ho they are labelled. Also beware that because many people use mpeg4 .movs, if you ask for advice about mpeg4 you might get people giving you settings that only show up when saving movs. Also if you already have video encoded as mpeg4 .mov's, it is possible to convert them to .mp4 files without having the reencode at all! This is potentially very important or useful to some people, so I will make a seperate message about this later. Regarding your audio, it all seems a bit odd to me. I listened to both of your clips, and the biggest difference appears to be the volume of the audio. I wouldnt expect the extreme difference in volume to be due to bitrate, unless something is malfunctioning. Maybe its to do with mono/stereo options. Is most of the audio on one channel rather than the other? Is it possible you changed any other audio setting for the 2nd version? Or maybe for some reason it is bitrate, but it shouldnt be as far as my brain knows. Audio with too low a bitrate should suffer from loss of detail and artefacts, just like video at too low a bitrate. But video isnt less bright with a lower bitrate, and thats the video equivalent to low volume? I prefer higher quality audio settings than many videobloggers use, in terms of Khz, but people vary greatly in how much fo the filesize they are prepared to accept being taken up by audio. The key is to match Khz and mono/stereo to an appropriate bitrate, just as with video the resolution and framerate will set boundaries on what a sensible bitrate to use is. I could say a lot more about this, but I wont right now as this emails getting too long already. If I have time, I would like to try to rewrite all of my encoding thoughts into a structured resource, and you and anybody else are welcome to reuse it. As I dont understand what Im saying myself on these issues sometimes, Im desperate to find ways to simplify this. If a newcomer to videoblogging is met with replies like mine in response to realtively straightforward questions, its a barrier to videoblogging. The existing guides that people have done are very cool, and Ive no doubt they have saved many may humans, many many hours of messing around. But Im never satisfied, I see that quite a few issues to do with encoding are more about personal preference, than technical limitations. So there needs to be choice, theres so many factors that there is not one answer to the encoding quesstion. I therefore like the idea of creating a variety of different encoding 'profiles', collections of settings to suit different needs. eg if the popular 320x240 15fps 600kbits/sec mpeg 4 settings had a name, it would be easy to refer to them quickly, and it would also show that they are one great option, not the only great option. Then there would be a profile for people who want extra-small filesizes, one for quality junkies, a few different HDV ones. Anyway Ive said more than enough for now. Steve of Elbows --- In firstname.lastname@example.org, JD Lasica <[EMAIL PROTECTED]> wrote: > Today I spent a little while experimenting with MPEG-4 settings. > Because some people prefer MPEG4 to QuickTime, I've been hoping to do > more of my video in mp4, but I've never been pleased with the default > settings. > > So, I thought I'd ask the wise people on this list for some advice or > pointers for MPEG-4 compression settings for publishing a video for > display on Ourmedia. (And, yes, I know all about Michael Verdi's PDF > primer on Video compression with 3iv ... ------------------------ Yahoo! Groups Sponsor --------------------~--> Fair play? Video games influencing politics. Click and talk back! http://us.click.yahoo.com/T8sf5C/tzNLAA/TtwFAA/lBLqlB/TM --------------------------------------------------------------------~-> Yahoo! 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