I have this old Sound Blaster X-Fi Extreme with Toslink in and for funsies I want to try to record 5.1 audio. I know you have to record 24 bit audio but what else? Just tried Audacity and I don't know if I did it right. Is this what it's supposed to look like?
I tried decoding an exported 24-bit wav with BeSweet but it's really hard to use the GUI. Stuff disappears and when I did get it working it errors out.
I checked the MediaInfo on the exported wav and even though I had Audacity export a 24-bit file, it keeps exporting a 16-bit file. Don't know if that's normal or not.
I would record 5.1 through HDMI through my Avermedia card but it doesn't seem detect 5.1 through my cable box's HDMI out, so I don't know if it's really outputting 5.1. I recorded this channel through firewire last year and it did have a 5.1 track though, so I'm not sure what's going on.Code:General Complete name : D:\recordings\5.1 test 96k.wav Format : Wave File size : 2.48 MiB Duration : 4 s 514 ms Overall bit rate mode : Constant Overall bit rate : 4 608 kb/s Audio Format : AC-3 Format/Info : Audio Coding 3 Format settings : Little Muxing mode : SMPTE ST 337 Codec ID : 1 Duration : 4 s 514 ms Bit rate mode : Constant Bit rate : 4 608 kb/s Sampling rate : 96.0 kHz Bit depth : 16 bits Compression mode : Lossy Stream size : 2.48 MiB (100%)
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Last edited by ENunn; 22nd Aug 2020 at 19:11.
Most video capture devices can only capture stereo audio. Only a few video capture devices can capture 5.1 audio. A handful of older Hauppauge video capture devices could capture 5.1 channel AC3 using Toslink or HDMI with the right software.
There was also a discontinued Korean HDMI video capture device that could capture 5,1 channel AC3 and there is a Magewell HDMI video capture device that can capture 5.1 channel AC3 audio but the process requires a fair amount of technical expertise. https://forum.videohelp.com/threads/392907-Is-there-a-lossless-video-capture-card-that...ures-5-1-audio
Note that a cable box's HDMI or Toslink audio output is often controlled by settings in its internal menus. The older Xfinity box that I had provided a choice between 2 channel LPCM or the AC3 audio in the broadcast.
Last edited by usually_quiet; 23rd Aug 2020 at 15:31. Reason: grammarIgnore list: hello_hello, tried, TechLord, Snoopy329
Toslink (aka optical fiber-based SPDIF, which is a consumer variant of AES3) only supports a limited bitrate (~2.5Mbps). So it is not capable of carrying 5.1+ multichannel audio in uncompressed form.
It is capable of carrying COMPRESSED (ac3 or dts) MC audio, but only when that compressed stream has been re-packetized to match the data rate of a standard stereo uncompressed stream. And then, it masquerades itself AS such a stereo stream.
So to capture, you would need to:
1. Record the 2 ch incomming "lpcm" stream
2. Save the stream as a "wav"
3. Convert the "wav" (aka repacketized compressed file) to a normal compressed file. So, dts-wav -> dts, or ac3-wav -> ac3.
Then you will have your normal 5.1. It will be compressed, no getting around that when using toslink.
Note that the removal of the null packets does not change the compressed data itself in any way, so no further degradation or loss.
There is one thing about the Hauppauge HDMI capture devices that capture AC3 that I forgot to mention. If they receive 2-channel LPCM audio, it is captured in AAC format rather than WAV.
Last edited by usually_quiet; 23rd Aug 2020 at 16:20.
What should I used to convert the wav though? I've been exporting as a 24-bit WAV and on some recordings just sends a 24-bit PCM file according to MediaInfo.
Last edited by ENunn; 23rd Aug 2020 at 18:01.
Toslink only supports up to 20bit LPCM. A compressed stream, such as ac3 or dts, is gonna be distinct from and independent of that limit. But by and large, most compressed streams (and the encoders that create them) seem to have 16bit source limitations, so am not sure you'd really be getting much more by trying to push for end to end 24bit support.
Not only that, but you say you don't care it's compressed, but that compression could be considered to be doing more damage to signal quality than the limiting from 24 to 16bit.
@usually_quiet, yes capture and direct, non-decoded playback would yield what would most likely be called digital "NOISE".
Bsconvert used to be able to do it.
Ignore list: hello_hello, tried, TechLord, Snoopy329
Sorry for the months late reply
For the TOSLINK output, if I change the audio coding format to Stereo, audio is fine but it's sped up. Everything else is just typical digital buzzing or whatever.
General Complete name : D:\recordings\toslinktest.wav Format : Wave File size : 3.42 MiB Duration : 6 s 219 ms Overall bit rate : 4 609 kb/s Audio Format : PCM Codec ID : 1 Duration : 6 s 219 ms Bit rate : 4 608 kb/s Channel(s) : 2 channels Sampling rate : 96.0 kHz Bit depth : 24 bits Stream size : 3.42 MiB (100%)