ESAI or S/PDIF for SPDIF stream

[atillametetured]

Greetings,

I have a question with the S/PDIF usage in I.MX6 processors. I know there is an S/PDIF  and also ESAI (Enhanced Serial Audio Interface) in I.MX6.

ESAI is compatible with SPDIF transceivers but the processor already has a module for SPDIF transmitter and receiver.

My question is, is SPDIF interface actually a part of ESAI (which I assume not) or is it a seperate interface? If they are seperate interaces, which would you suggest

using for streaming 5.1/7.1 audio or stereo sound? I assume that using the ESAI and an extra transceiver will reduce the burden on the processor while increasing

the cost, but does it also increasing the programming work, is ALAS okay with me using ESAI for SPDIF or do I need to come up with a driver for that? Or would you

just suggest me using the SPDIF interface for its designated purpose.

I have to note that asides from acting as an audio streamer, the proposed system might also be streaming HD vidoe through HDMI and performing other network control

bussiness in the meanwhile so the processor will be quite busy.

Thanks in advance,

Mete

Message was edited by: Atilla Mete Turedi

[igorpadykov]

Hi Atilla

SPDIF interface is not part of ESAI. 7.1 audio is supported by Linux BSP,

using 7.1 CODEC (cs42888), refer to sect.28.2 SoC Sound Card attached Linux Manual.

CONFIG_SND_MXC_SPDIF option provides support for the HDMI Audio driver,

sect.16.3.1.

Best regards

igor

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[atillametetured]

Hi Igor,

Thanks for your reply

7.1 audio is supported by Linux BSP, using 7.1 CODEC (cs42888)

First of all, what do I need this codec for? SPDIF can carry 7.1 compressed audio (Dolby or DTS). What

is the codec going to do? All I want to do is transmit surround sound, say of a movie, which is already compressed

according to Dolby or DTS.

Also when you say 7.1 audio is supported by Linux BSP using 7.1 codec (CS42888),

does this imply no codec IC is required for 5.1?

refer to sect.28.2 SoC Sound Card attached Linux Manual.

can't see any attached Linux Manual?

Thanks,

Atilla

[igorpadykov · Accepted solution]

Hi Atilla

for obtaining attachment click on red in previous answer

I agree that SPDIF can carry 7.1 but I am afraid Linux does not

support it,  5.1 too, only 7.1 using cs42888 is supported.

Note, Dolby codec is "Restricted Distribution" which requires agreement to be in

place with Dolby for the specific technology prior to accessing,

in order to comply with 3rd party requirements.

Best regards

igor

[atillametetured]

Hello Igor,

Okay what I understand from what you just said is:

Technically and physically it is possible to transmit 5.1 and 7.1 surround sound using only the S/PDIF Interface

found on the i.MX6Q without the need for a codec. However because ALSA did not implement it yet, you have to

use a codec and only be able to transmit 7.1 sound.

This brings us to the question: So it is possible to write your own driver for the SPDIF interface and not rely on ALSA

to transmit (just transmit, decoding and uncompressing will be performed by the surround system, which I believe is how it normally works, please confirm) 5.1 and 7.1 compressed Audio (DTS or DOLBY) given that you made the agreements to access their data?

(Which I find weird because, if I have a movie with a dolby sound, which I purchased, I obviously purchased

the sound with it). However this is the subject of a different topic.

Thanks,

Atilla

[igorpadykov]

HI Atilla

yes I believe it is possible to write own driver for the SPDIF interface

for transmitting 5.1 and 7.1 compressed Audio.

~igor