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Topic: I'm crazy-- I want AC3 RF Mode (Read 4368 times) previous topic - next topic
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I'm crazy-- I want AC3 RF Mode

All right chaps, I work in an engineering dept of a tiny tv station with "no budget" -- their words.

We have a dot-2 digital subchannel which consists of a server box, satellite IRD, and playlist that adds a few minutes of automatically triggered local commercials from that server box.

The box is pretty dumb, and requires sd (480i) MPEG2 video and 2 channel stereo AC3 audio at 192k with very specific PIDs etc.  It seems to pass these files without processing them further.

We had a great ffmpeg preset but it recently came to our attention our local breaks were quiet on an ATSC set-top box, even though they're great on our reference demod and my own home 32" tv.

I have a PVR that records to an external USB drive and have recorded both the network feed and some local breaks.  Making headway in matching their specs.  (Network tech support is helpless BTW).

Dialnorm -27... check.
DRC... they have it, we used to not.  Aha!
I implemented an ffmpeg batch file that splits off the audio, Aften.exe puts compression on it, then ffmpeg splices the audio back in without further encoding.  Perfect!  Except the Dolby curves smoosh what we have, even quieter.  And yes our dialnorm setting matches our average speech audio.

If I were to take "some of theres" and "some of ours" and play it back on VLC they match, audio-wise.  If I play an aircheck AC3 on a computer, it matches fine going in and out of local breaks.  If I listen to a set top box either thru the RF out or the RCA outs, they're quiet. 

Long story short, is there something (freeware) like Aften that will add an "RF Mode" flag?  I'm promised a tantalizing 11 dB of boost, only on the boxes that need it.    And yes, I have to keep in mind CALM act compliance.

I'm crazy-- I want AC3 RF Mode

Reply #1 –
BTW the other free tools that work pretty slick in my workflow are

azid.exe which will rip through an hour plus ac3 in mere seconds, noting whenever there's a change in dialnorm, copyright flag, etc.  Helps me catch errant, old stuff that might still be airing.

Aften, as is gushed over on "another forum" and maybe this one too.

Leeaudbi, which does everything azid does, plus goes through every frame showing compression effects/ bias/ whatever you want to call it.

Orban has a neato LKFS measuring loudness monitor that will monitor one's sound card out (absolute digital-- very precise) as well as a sound card in, very impressive.

128gain, which can sit in a batch file and automatically pull content up or down to the correct LUFS, which for all intents and purposes matches LKFS over 30 seconds.

I'm crazy-- I want AC3 RF Mode

Reply #2 –
Thanks for the recommendations! There’ll be readers who will find those useful.

Someone else split away the other posts before, so I’ll add this free bump