Does ffmpeg offer AAC decoding and PCM output to receiver?

dooferdog

Member
Hi all

I have a number of mp4 files with AAC encoded 6 channel audio. I can stream them over my network or from USB onto my HDR with custom firmware, but it's not clear to me what audio is being output to my receiver. My 'info' option on the receiver suggests PCM input but how can I tell what is really being output?? Any suggestions apprecaited.

Cheers
 
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dooferdog

Member
Alternatively, can the Humax be forced to play mkv files which sometimes contain AC3 encoding instead of AAC?
 

HarveyB

Active Member
How is the humax connected to the receiver?
HDMI or Optical or phono(??!)?
You also need to make sure that "Settings>preferences>audio" is set to multichannel.

Doesn't your receiver indicate when it is outputting multichannel (5/1, 2/0, ...)?


Sent from my iPad using Tapatalk HD
 
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dooferdog

Member
Hi Harvey

Humax is connected via HDMI. I'm sure the audio prefs are set to multi channel but I will check; I certainly receive multi channel input to the Yamaha receiver when playing Freeview recorded HD content for example. Since posting I have identified that when playing the mp4's My Yamaha receiver shows a 2 channel PCM input. With this input I can then chhose any number of DSP's to output but they are all pseudo surround (ie. not very good) , not native "straight" mutlichannel DTS etc.I believe the Humax is downmixing to 2 channel PCM before outputting to the Yamaha. From some google searches I believe there is a problem with lack of AAC decoders on most consumer kit, but I'm intrigued why the Humax appears to be doing the downmixing. I could be completely wrong though.
 

Ezra Pound

Well-Known Member
I have a DD5.1 MKV file on my Humax (converted from a Hi-Def *.TS file) that retains it's 6 channel sound when played on the Humax into an AV amp, so the Humax will output DD5.1 from non TS files, however my MKV has AC-3 sound rather than AAC.

On a slightly different topic I have found that TS files recorded on the Humax containing DD5.1 sound will only playback in stereo if the sidecar files are missing, there must be something in them that is required to enable DD5.1 playback, this is obviously not related to your problem though
 
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dooferdog

Member
Oh wow, I'm sure MKV files won'y play on my Humax. Perhaps whether one will play or not is related to the options used to encode it in the first place?
 

Ezra Pound

Well-Known Member
MKV is a container, what is inside can vary a lot, here is are the details of the MKV that I played :-

mkv-info.jpg
 

HarveyB

Active Member
Dooferdog, be aware i am not an expert on the different file formats so you may be way ahead of me.
Just a couple of ideas:
- have you tried using the optical link between the two devices. Assuming your receiver supports it and you have an optical cable?
- have you checked the settings on the receiver itself?
- does the receiver literature say whether it handles AAC multichannel?


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Ezra Pound

Well-Known Member
It's probably worth pointing out that the Humax also has a smaller list of playable formats when the file is streamed to it rather than the file being resident on it's hard drive
 

fenlander

Active Member
I'm told it's something to do with compression of the file headers (?). Compressed headers became a default for web-posted mkv files a couple of years ago; older mkv files play on the Humax, newer ones don't - unless you code them yourself using software that doesn't do the compression.

The Hummy does not crash on AC3 audio per se. I've re-muxed mkv files to mp4 while preserving both the video and audio streams and those with AC3 audio do play after remuxing. However, recoding the audio to AAC gives much better sound levels. Try GotSent or Xvid4PSP5 for quick remuxing to mp4.
 

mihaid

Well-Known Member
The Hummy does not crash on AC3 audio per se. I've re-muxed mkv files to mp4 while preserving both the video and audio streams and those with AC3 audio do play after remuxing. However, recoding the audio to AAC gives much better sound levels. Try GotSent or Xvid4PSP5 for quick remuxing to mp4.
Cool, so what settings for the output file do you use in Gotsent so that the hummy plays it with 5.1 surround.
 

Ezra Pound

Well-Known Member
Handbrake will take an MKV as an input file but I don't know if it will un-compress a compressed header, give it a try, it's free to download
 

Ezra Pound

Well-Known Member
As fas as I can remember :-
Presets : Regular - Normal
container : MKV (but MP4 also OK)
Video filters : All off
Video : H.264(x264)
Framerate : same as source
Quality : constant (RF:20)
Audio : AC3 passthru
Advanced : all default
 

fenlander

Active Member
Cool, so what settings for the output file do you use in Gotsent so that the hummy plays it with 5.1 surround.
For better control over the audio, I'd suggest Xvid4PSP5 - GotSent is quicker, but minimal. I don't use 5.1 myself, but in Xvid4PSP5 you can set the video to Copy and control the audio recode as you wish.
 
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dooferdog

Member
Thanks for all the input everyone. I have been very busy and ill this week so sorry for notvrespkndinv to some of the questions.

I havent had much chance to move things forward testing and setup wise, but in essence I am most interested in not having to do anything in terms of recoding files but would be prepared to look at the xvid4psp5 and gotsent suggestions.
I would prefer to understand if there was any chance the CF could include a mod to enable streamed MKVs to play, as these invariably seem to have AC3 encoding already but just wont play.
Thanks
 
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