The Audio FAQ for ADV7842 and ADV7604

Document created by PaulS Employee on Oct 30, 2012
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1. Does ADV7842 say Audio sample packet detected in case incoming signal is PCM or IEC61937 as explained in page 219 (UG-214.pdf). If so, how we can further detect between PCM and AC3.

[ANS] The audio sample packet detect (HDMI map, 0x18 [0]) will be automatically set high when PCM and IEC61937 audio is received. Also in the HDMI map, 0x36[1] will be cleared to 0B if PCM data is received in the audio sample packets. This bit is set to 1B if compressed audio is received in the audio sample packets (Dolby 5.1, ACC3, etc. )

2.      Is “Audio mode change status interrupt” mapped to INT1 or INT2

[ANS] Yes it can be, see the interrupts section in the hardware manual.

3.      Right now for PCM, we are using AP1 pin connected to I2S data on main processor side. In case of AC3 which output interface has to be used

[ANS] The preferred output for AC3, is SPDIF. SPDIF is output on AP0. AP1 to AP4 generally carry I2S data and their output will be muted if compressed audio is received and the mute compressed audio bit is set to 1B (HDMI map, 0x14 [5]).

4. Do we need to change the output interface depending on the incoming data PCM or AC3?

[ANS] We would recommend using SPDIF for compressed audio and I2S for not compressed.

5. In case incoming data is multi channel compressed audio say 5.1. Is it possible to convert into stereo (2-channel) using 7842.

[ANS] no it is not, we do not decode Dolby audio. All the HDMI receiver does is take the audio data from the audio sample packets and places it into an SPDIF stream at the output.