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Thread: MM compression

  1. #1
    Programmer Bulat Ziganshin's Avatar
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    how much channels wave file can have? i think that 1 2 6 8 are possible values. something else?

    and how can i decode .ac3 file?

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    The Founder encode's Avatar
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    Quote Originally Posted by Bulat Ziganshin
    how much channels wave file can have?
    1...65535 are valid values. However, as a rule, WAVE files often has 1 (Mono) or 2 (Stereo) channels.

    Quote Originally Posted by Bulat Ziganshin
    and how can i decode .ac3 file?
    Use Google!

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    Don't know about channels... regarding ac3 to wav, I've found one opensource decoder.

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    Programmer Bulat Ziganshin's Avatar
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    i need just to decode ac3 file from your testset

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    Programmer Bulat Ziganshin's Avatar
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    Quote Originally Posted by encode
    1...65535 are valid values.
    it may take a bit too long to test all these values. even if each channels/bytes combination is checked in 1/100th of second

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    Quote Originally Posted by Bulat Ziganshin
    it may take a bit too long to test all these values. even if each channels/bytes combination is checked in 1/100th of second
    You can read the header. Anyway, assume that WAV has 2 channels at max.

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    Programmer Bulat Ziganshin's Avatar
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    it's for situations when header can't be used. i don't want to make such assumption because one of tests includes 6-channel file and afaiu it's the wave file converted from ac3 (that i have downloaded and now want to decode)

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    The Founder encode's Avatar
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    When check for:
    1 (Mono)
    2 (Stereo)
    6 (5.1)
    channels.
    By the way, some time ago, I had an idea about searching header inside any file. How to detect WAV:
    Search for "RIFF" id. After read the RIFF size (4 bytes). After check for "WAVE" id. And here you can read the header and you know the real WAV file size. All simple.

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    Programmer Bulat Ziganshin's Avatar
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    also 7.1 channels exist afaik

    about RIFF - the real problem is how then invoke tta on this part of file while using other algorithm on the rest. instead of particular solutions, i plan to change archive structure so that parts of one file may be compressed by several algorithms plus add data type detectors as in rar

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    Quote Originally Posted by Bulat Ziganshin
    i need just to decode ac3 file from your testset
    my testset?

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    Programmer Bulat Ziganshin's Avatar
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    well, i don't remember exactly. someone's testset includes 6-channel ac3 file converted to wav

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    The Founder encode's Avatar
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    Quote Originally Posted by Bulat Ziganshin
    also 7.1 channels exist afaik
    Yepp. 7.1 channel surround sound.

    Quote Originally Posted by Bulat Ziganshin
    someones testset includes 6-channel ac3 file converted to wav
    Someone complained about benchmarks - like "we create compressors for real life and for real users, all benchmarks are liars..."

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    The Founder encode's Avatar
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    Anyway, to get even true 5.1 at home you must be a crazy millionaire and it's not related to PC anywhere. I can generate WAV file with 1000 channels, what's next? In PC shops I saw some fun stuff which they called surround speakers, with subwoofer. It's shit. The real surround sound you can find at cinema, and how much it costs? And how about sound design of room (isolation, acoustic design, etc.) At my theatre studio we got two proffesional sound monitors, each of them costs 4000 US... To get crear stereo sound you need 8000 US plus, a professional sound card 1000+ US, sound mixer 8000+ US, pro amplifier, plus specially designed room, and other related stuff, concluding, even simple professional studio gets above 100,000 US... and it's only about recording. About cinema, it's crazy, you also must have a licensed sourround sound decoder along with CRAZY rider. Note that at middle sized theatre (700+ spectators) where I'm working, totally sound gear costs above 1,000,000 US. Mixers, microphones, amplifiers, equalizers, sound processing, monitors, stage constructions, etc. Even simple FOH sound board (mixer) costs 100,000 US. Can you get it at home? Along with professional staff to operate with such things...

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    Quote Originally Posted by encode
    true 5.1 at home
    for most users this = I know if the sound comes from front/back and/or from left/right + I have something to do the bass stuff

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    Programmer Bulat Ziganshin's Avatar
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    that's great. thank you!

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    Programmer Bulat Ziganshin's Avatar
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    Quote Originally Posted by encode
    Someone complained about benchmarks
    its still true. the real question is time required to implement all these useless features. im pretty sure that noone will save 6-channel sound in plain wav file but as far as adding its support is just two chars in program, i can implement it

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    Programmer Bulat Ziganshin's Avatar
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    also, which extension raw mm files may have? just now i select bitmaps by bmp/tiff and waves by wav/pcm/aiff extensions

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    Searching here: http://wiki.multimedia.cx/index.php?title=Category :Container_Formats and here: http://en.wikipedia.org/wiki/WAV can help. But sometimes those extensions are just container formats and can content comressed data too

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    Programmer Bulat Ziganshin's Avatar
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    well, i have found tga and au there. something else? in particular, which extensions has raw graphics files produced by digital cameras?

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    My mencoder http://www.mplayerhq.hu/design7/info.html claims it supports 107 audio & 227 video codecs.
    It comes with mplayer http://tirnanog.fate.jp/mirror/mplayer/ and its sources are open http://www.mplayerhq.hu/design7/dload.html

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    Programmer Bulat Ziganshin's Avatar
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    Quote Originally Posted by nimdamsk
    such list is pretty useless for me - it doesnt say anything about fromats. i need to include here only raw uncompressed formats

    Quote Originally Posted by nimdamsk
    http://en.wikipedia.org/wiki/RAW_image_format
    great! unfortunately, it says nothing about compression

    Quote Originally Posted by nimdamsk
    My mencoder
    is it possible to get list of extensions of uncompressed MM formats?

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    It can't, unfortunately.
    AFAIK many media containers can support both compressed and uncompressed data. For example avi, bmp, mov, tga, gif, png, tiff. So, you should explore their headers, and i think you won't like it
    There is unsolved problem with huge MM data storage - DV (Digital Video) compression http://en.wikipedia.org/wiki/DV If someone invent lossless DV compression engine, imho it would have commercial success.
    I think that nowaday's MM data is kept mostly compressed, lossly or lossless. Even game's data is compressed with some lossless algo. There are comparatively narrow niches, mostly in professional spheres. Good thing is that professionals mostly are solvent

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    Programmer Bulat Ziganshin's Avatar
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    of course. i'm sure that MM compression is pretty useless thing, but afair you was among those who want to see it implemented in archivers?

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    Quote Originally Posted by Bulat Ziganshin
    also, which extension raw mm files may have?
    Some common extensions:

    RAW, PCM - possibly, 16-bit signed, Stereo, 44100 Hz
    SAM, SB - 8-bit signed, Mono, 8000 Hz
    UB - 8-bit unsigned, Mono, 8000 Hz
    UW - 16-bit unsigned, Mono, 8000 Hz
    SW - 16-bit signed, Mono, 8000 Hz
    UL - 8-bit signed, u-Law encoded, Mono, 8000 Hz


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    Quote Originally Posted by Bulat Ziganshin
    of course. im sure that MM compression is pretty useless thing, but afair you was among those who want to see it implemented in archivers?
    Yes, i was Chtob ne huzhe chem u drugih
    Seriosely, nothing prevent you from making niche compressor and earning some cash And you can forget about all those old audio and image formats, just because those days files were small and they cant really improve compression rate. WAV, TIFF, TGA, BMP - most spreaded types - would be enough. And some types from MAC platform.

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    Programmer Bulat Ziganshin's Avatar
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    i always said that best way to convince users that they don't need MM is to implement it ditto about MFC test

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