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6th March 2012, 16:48 | #3 | Link |
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MPEG Multichannel is an extension to the MPEG-1 Layer II audio compression specification, as defined in the MPEG-2 Audio standard (ISO/IEC 13818-3), which allows it provide up to 5.1-channels (surround sound) of audio. To maintain backwards compatibility with the older 2-channel (stereo) audio specification, it uses a channel matrixing scheme, where the additional channels are mixed into the two backwards compatible channels. Extra information in the data stream (ignored by older hardware) contains signals to process extra channels from the matrix.
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6th March 2012, 18:17 | #5 | Link |
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It's use never really caught on...
As far as compressed multi-channel audio formats go, AC3 took the high ground very quickly. Most probably because hardware decoders were already available.
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8th March 2012, 08:16 | #9 | Link |
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I dint try mediainfo. I dont need a software instead i need a method to identify multichannel extension.
Do i get that info in any of the desciptors or should i parse the audio frame? I dont want to parse the audio frame (except header) because it takes lots of resource in my hardware. I can parse header if required. |
14th December 2023, 18:37 | #11 | Link | |
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resurrecting the thread to provide some news
i tried MediaInfo on an actual MPEG Multichannel file, and here's what it gave me Quote:
however, this file was encoded from a lossless 5.1ch wav file to a mp2 file using one of the MPEG Multichannel encoders available on this site Last edited by modus-ms325c; 14th December 2023 at 20:36. Reason: oops can't show off my private info here, sorry my mistake |
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15th December 2023, 02:43 | #12 | Link | ||
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Maybe look at the amount of ancillary data using Mp3GuessEnc. Other software like radio playout systems may write some extra data, but is usually less. The Fraunhofer encoder doesn't format unspent bytes as ancillary, but Lame does.
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15th December 2023, 04:33 | #14 | Link | |||
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sure thing, i'll PM you shortly Last edited by modus-ms325c; 15th December 2023 at 04:51. Reason: address ivanb's reply and |
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15th December 2023, 04:50 | #15 | Link |
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Ancillary data is where extensions to the mpeg audio format are saved. If you can't parse it, you can guess by the size. MPEG multichannel has about 192 kbit/s for the stereo downmix, and 192 kbit for the extension.
Sample files: http://j7n.sytes.net/temp/mpegsurround/ I could only get the pub_enc encoder to accept a 16-bit 6ch AIFF input file. You could look at how mp3guessenc for an example, since it is open source. It detects multichannel in Layer II. Last edited by j7n; 15th December 2023 at 04:53. |
15th December 2023, 04:53 | #16 | Link | |||
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Wav2Mpg. ring a bell? Quote:
i tried to compile it myself (using both MSYS2 MINGW32 and MSYS2 MINGW64, respectively) but it threw up an error instead. Last edited by modus-ms325c; 15th December 2023 at 05:00. |
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29th December 2023, 16:14 | #17 | Link | |
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Last edited by SeeMoreDigital; 29th December 2023 at 16:18. |
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29th December 2023, 17:08 | #19 | Link | |
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Even as a 2-channel format, it's rubbish!
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29th December 2023, 20:25 | #20 | Link |
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Decoding with pub_dec from the linked site (hosted on really rare wares) yields a multichannel output with a separate LFE with low sampling rate. There is some crosstalk. And the bandwidth is limited to 14-15k, which is what you'd expect from 192 kbit/s.
This format doesn't seem to have reason for existing. At the time MPEG multichannel was created, AC-3 was already mature and widely supported, and it was a step backwards with the non discrete downmix approach. Why pick it out today, just to pick a fight. I was surprised that the mp3guessenc dev has deciphered the headers. |
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