I'm new to this forum and this is my first post so please forgive me if I ask stupid questions.
My question is as follows. I have a collection of MP4 video files but I wanted to convert them to either MPEG or AVI or some format that is more commonly used on computers than MP4. I know VLC player as well as other players can play MP4 files easily but I wanted these in a format that is easy for complete computer novices to play on their computers. The content of these videos is simply audio plus text. Anyway, I have tried various conversion tools and they work fine except that the quality of the video (the clarity of the text) deteriorates considerably if I tweak the settings of the conversion utility to produce an output file of similar size to the input file. The only way I have found of producing good quality audio and video output is by selecting sampling rates etc that produce an output file that is much larger than the input file. As an example I have an MP4 file that is 7 megabytes in size and I produced an MPEG file that is of perfect quality but it is 150 megabytes big!
Does anyone know if it possible to produce a file of similar size (twice of three tmes as large is fine but no more) but also of similar quality? Perhaps there is some trick that can be used specifically for video containing text?
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First of all any conversion from one type to another usually involves SOME quality loss. That is unavoidable. How much depends on bitrate used and destination source.
Some programs to try:
Those are just two that are widely used here. There are many others here in the tools section:
Also you can use the videohelp bitrate calculator to determine file size - though I don't know if its been updated for conversion from mp4.Donatello - The Shredder? Michelangelo - Maybe all that hardware is for making coleslaw?
Using the original source that the .mp4 was derived from would be a good idea. This way you don't have 2 rounds of quality loss.
MPEG2 has poor compression, so you need a large filesize (bitrate) to compensate
XviD/DivX is better than MPEG2, but the codec that offers best compression is AVC/h.264 . It doesn't always work too well in the .avi container, you're better off with .mkv or .mp4 containers...
Depending on what is inside your .mp4 (probably AVC) you are probably going from a efficiently compressed source to a more lossy/worse compression codec - that is your problem.
The problem is that I don't have the original source. How would I check what is indide my MP4 container? If it is AVC then should I use AVC/h.264 compression?
You can use mediainfo
If you are willing to sacrifice quality for compatibility then by all means use MPEG2 and the filesize will be much larger - as you noticed. But note even MPEG2 won't play natively on Windows systems - you need a codec installed for that too. The only format that will play with WMP natively is WMV. (assuming that WMP is the most commonly installed player on Windows systems).
You can try AVC2AVI to force AVC streams into .avi container, but playing that back doens't always work (although it works most of the time) - at least this way you don't re-encode. However, if your audio is AAC, this won't work because AAC is not supported in .avi containers. If your "novices" don't have the appropriate splitters/decoders installed - this won't work either.
I would leave it as is. .mp4 is very common these days, all the Apple formats (e.g. Ipod etc..), portable media players, PS3, PSP, XBX360, many smartphones etc... support many audio & video formats in .mp4
poisondeathray has it here. WMV (and I guess MS MPEG-4 and MPEG-1) is the only natively supported format that won't ever require installation of further components. Even Windows XP doesn't include an MPEG-2 decoder (though admittedly most retail PCs include one from PowerDVD, etc). For maximum compatibility you should even consider going to WMV8/WMA2 in an ASF container to reach people without WMP10/11 installed.
With all that said, though, poisondeathray is also right about .mp4: since people will likely have to install SOME decoder anyway, you might as well leave it as .mp4, which can be decoded with a variety of solutions.
What will be your method of distribution for these files? Are these training videos, etc.? Will the recipients of the video's be able to install a media player/codec on their machine? Once we know this info I'm sure a suitable solution can be found.