[alsa-devel] IEC61937/SPDIF
Hi All, I have to develop driver for SPDIF output of my board connected to HDMI.
I'm not sure for following (specially IEC61937) 1) How should driver know if it is compressed audio or plain pcm 2) Is their any plugin available for IEC61937, I could see only for IEC958 3) Who should create burst preamble, some plug in or driver.
Thanks and Regards, Ajay
On 14.06.2011 15:47, ajay khandelwal wrote:
Hi All,
Hi!
I've worked with IEC61937, but I'm no ALSA expert, so I hope others correct me if I'm wrong.
I have to develop driver for SPDIF output of my board connected to HDMI.
I'm not sure for following (specially IEC61937)
- How should driver know if it is compressed audio or plain pcm
You can look at the bit 1 (0x02) of AES0 IEC958 channel status.
The driver generally provides IEC958 controls: http://www.alsa-project.org/~tiwai/writing-an-alsa-driver/ch10s03.html That are then used via hooks in "foo.pcm.hdmi.0" (or "foo.pcm.iec958.0" for non-hdmi) definition in /usr/share/alsa/cards/foo.conf (look at existing drivers for examples). Applications can then set these flags by e.g. opening the ALSA audio device as "hdmi:AES0=0x06,AES1=0x82" etc.
- Is their any plugin available for IEC61937, I could see only for IEC958
No.
- Who should create burst preamble, some plug in or driver.
Currently they are created by the applications themselves.
At Tue, 14 Jun 2011 21:09:43 +0300, Anssi Hannula wrote:
On 14.06.2011 15:47, ajay khandelwal wrote:
Hi All,
Hi!
I've worked with IEC61937, but I'm no ALSA expert, so I hope others correct me if I'm wrong.
I have to develop driver for SPDIF output of my board connected to HDMI.
I'm not sure for following (specially IEC61937)
- How should driver know if it is compressed audio or plain pcm
You can look at the bit 1 (0x02) of AES0 IEC958 channel status.
The driver generally provides IEC958 controls: http://www.alsa-project.org/~tiwai/writing-an-alsa-driver/ch10s03.html That are then used via hooks in "foo.pcm.hdmi.0" (or "foo.pcm.iec958.0" for non-hdmi) definition in /usr/share/alsa/cards/foo.conf (look at existing drivers for examples). Applications can then set these flags by e.g. opening the ALSA audio device as "hdmi:AES0=0x06,AES1=0x82" etc.
- Is their any plugin available for IEC61937, I could see only for IEC958
No.
- Who should create burst preamble, some plug in or driver.
Currently they are created by the applications themselves.
There is also iec958 alsa-lib PCM plugin. But this is usable only for drivers that can take IEC958 subframes as the supported format.
Takashi
participants (3)
-
ajay khandelwal -
Anssi Hannula -
Takashi Iwai