Add "TX Digital Audio Gain" to ADTS headers

[Sussyman2-0]

https://hdradio.com/broadcasters/engineering-support/properly-adjust-time-and-level-alignment/

this allows you to set a "loudness" to match both a heavily dynamically compressed analog FM signal with a raw digital signal. I know this is a feature inside the FDK-AAC encoder which i will attempt to add myself. but im curious if you want to take a crack at it.

https://www.nrscstandards.org/standards-and-guidelines/documents/standards/nrsc-5-d/reference-docs/1017s.pdf

this is the spec for the HDC headers and other things.

“For audio stream ID 0b00, bits in the header provide the TX Digital Audio Gain parameter. For MPS (main program service), this defines the audio level adjustment the receiver applies to equalize digital vs analog loudness. For SPS (multicast), it defines adjustment to equalize digital program loudness relative to other digital programs.”

[TheDaChicken]

I know this is a feature inside the FDK-AAC encoder which i will attempt to add myself

"TX Digital Audio Gain" is a field in PDUs. HDRadio doesn't use ADTS transport. ADTS is used in gr-nrsc5 to encapsulate packets from faad2. There is no documentation on the HDC codec.

This can be modified here:

gr-nrsc5/lib/l2_encoder_impl.cc

Line 190 in 8a0ff82

/*digital_gain_or_per_stream_delay*/ 0,

This field should only be set when the stream id is zero. (gr-nrsc5 has no concept of the enhanced stream so that shouldn't matter).

[Sussyman2-0]

I know this is a feature inside the FDK-AAC encoder which i will attempt to add myself

"TX Digital Audio Gain" is a field in PDUs. HDRadio doesn't use ADTS transport. ADTS is used in gr-nrsc5 to encapsulate packets from faad2. There is no documentation on the HDC codec.

This can be modified here:

gr-nrsc5/lib/l2_encoder_impl.cc

Line 190 in 8a0ff82

/*digital_gain_or_per_stream_delay*/ 0,

This field should only be set when the stream id is zero. (gr-nrsc5 has no concept of the enhanced stream so that shouldn't matter).

Thank you so much about this explanation, its already implemented! How would i det the values? Do I paste the bit values in my above graph when I need to change it??
I will do some experimenting when I get my HDC patch working fully with PS! I really appreciate it!

[TheDaChicken]

You just provide the integer value between +7 to -8 to write_control_word.