HDMI - SPDIF convertor

[judderod]

My ideal setup would be a box that can split HDMI to one SPDIF out per channel. There would be a single channel DAC mounted right next to or on the back of each speaker, along with an amplifier. Thay way the analog lines are kept as short as possible, and there is no need for fancy analog cables that go the distance between the processor/receiver and each speaker.

It might be possible to tap into the I2S lines of a HDMI device and add a module that converts each I2S channel into a mono SPDIF (so the signals can be sent the distance to each speaker). Each DAC on the receiving end would need to be configured to accept a mono SPDIF signal.

[pingfloid]

Hi.

The HDMI to video + SPDIF converters are now on Ebay for around $43.

Since Android devices still do not officially support the connection of a USB DAC, I am thinking about this alternative to extract digital audio (2 channels only) from a tablet with HDMI output.

Do you know if the quality of the Digital Audio is not affected? Just the same as a regular coax digital output?




Thank You

ps:

If you have a spare click, please vote to increase the priority to implement the feature of the USB_CLASS_AUDIO compliant device DAC feature on Android devices :-)

http://code.google.com/p/android/issues/detail?id=24614

You need to be registered on google mail, and click vote at the bottom of the page

[abraxalito]

Thanks for the heads up - done.

[judderod]

Originally Posted by pingfloid

Do you know if the quality of the Digital Audio is not affected? Just the same as a regular coax digital output?

SPDIF does not support uncompressed multichannel audio. The highest rate it supports IIRC is 192KHz 24 bit x 2 channels. HDMI can support the same over 8 channels, maybe more. So the output from this device will be similar to using the SPDIF or Optical output from your source player - compressed.

[Saturnus]

Originally Posted by judderod

SPDIF does not support uncompressed multichannel audio. The highest rate it supports IIRC is 192KHz 24 bit x 2 channels. HDMI can support the same over 8 channels, maybe more. So the output from this device will be similar to using the SPDIF or Optical output from your source player - compressed.

Much lower in fact. One has to remember that SPDIF is an ancient very outdated standard.

If you follow the SPDIF standard it's 20 bit 48KHz max for PCM. The 4 extra bits for are an optional extension that most recievers will understand but not all. You risk LSB cut. Many SPDIF recievers can also recieve 96KHz but that is entirely not standard and you risk sample drops.

The SPDIF signal has a max standard transfer rate of 3.1Mbps. Even the lowly old USB 1.1 standard has 4 times that transfer rate capacity.

[macboy]

Originally Posted by Saturnus

Much lower in fact. One has to remember that SPDIF is an ancient very outdated standard.

If you follow the SPDIF standard it's 20 bit 48KHz max for PCM. The 4 extra bits for are an optional extension that most recievers will understand but not all. You risk LSB cut. Many SPDIF recievers can also recieve 96KHz but that is entirely not standard and you risk sample drops.

The SPDIF signal has a max standard transfer rate of 3.1Mbps. Even the lowly old USB 1.1 standard has 4 times that transfer rate capacity.

S/PDIF is standardized as IEC60958-3, and it supports up to 192 kHz at up to 24 bits per sample. Rates higher than 192 kHz are also supported for encapsulated data transfer, but not for raw PCM audio samples. Some older equipment was limited to around 6 Mbps, which placed a limit to 96 kHz (always 64 bits transmitted per audio sample x 96 kHz ~= 6 Mbps). It is always possible that older equipment will truncate lower bits.