Kodi AC-4 (GitHub) for Windows (for ATSC 3.0 TV)

[mvallevand]

I am glad it works for you but the @ferrels Kodi branch I read about apparently was based on an older version of Nexus that spams the server. Version 20.2.1 of pvr.nextpvr is highly recommended and earlier versions for Nexus are not supported.

When producing Kodi builds I suggest it would be wise to target Matrix or if possible create nightly for Nexus. There are exciting things coming often now.

Martin

[DSperber]

In passing, I believe I've discovered a problem with Kodi AC-4 as far as the sequence of channels in the AC-4 FFMPEG-decoded output. I was doing a complete matrix of tests tonight, using all available client apps on all available platforms (that I have available to me), documenting the type audio output (if any) and whether it was 2.0, 5.1, or faux-5.1 (i.e. the SD version).

There is a thread on the SD forum discussing copying ATSC 3.0 MPG/TS recordings containing imbedded AC-4 5.1 and replacing it in the output with transcoded AC-3 5.1. In that discussion there was the topic of the ChannelMap operand for FFMPEG. The correct sequence of channels expected by all external hardware and AVR's is 5.1 is L, R, C, LFE (SW), LS and RS. And in order to produce that channel sequence you must specify : "channelmap=0|1|4|5|2|3:5.1(side)".

I think Kodi AC-4 is incorrectly invoking FFMPEG with "channelmap=0|1|2|3|4|5:5.1(side)", which swaps the final two pairs of channels to be incorrectly ordered from what is expected. 0,1,2,3,4,5 may be the natural order, but the external world expects it to be 0,1,4,5,2,3.

It can easily be seen visually. When Kodi is set to "pass-through" to send its decoded output to the external audio system via HDMI, here is what is shown for the AC-3 version of 5.1 out of Kodi AC-4 (on the left) and AC-4 version out of Kodi AC-4 (on the right):

      


Looking at it from the perspective of the Windows PC itself (on which Kodi AC-4 is running), when the audio output is instead directed through DirectSound to the 5.1 speakers attached to the PC it looks like this. Again, AC-3 on the left and AC-4 on the right.

     

NOTE: there is an accidental unintended attachment to this post. I've tried to delete it but the forum software refuses to delete is when I push"update post". It's just stuck. Please disregard that attachment (or, if a Moderator could remove it I'd appreciate it). Sorry for the distraction.

[ferrels]

In passing, I believe I've discovered a problem with Kodi AC-4 as far as the sequence of channels in the AC-4 FFMPEG-decoded output. I was doing a complete matrix of tests tonight, using all available client apps on all available platforms (that I have available to me), documenting the type audio output (if any) and whether it was 2.0, 5.1, or faux-5.1 (i.e. the SD version).

There is a thread on the SD forum discussing copying ATSC 3.0 MPG/TS recordings containing imbedded AC-4 5.1 and replacing it in the output with transcoded AC-3 5.1. In that discussion there was the topic of the ChannelMap operand for FFMPEG. The correct sequence of channels expected by all external hardware and AVR's is 5.1 is L, R, C, LFE (SW), LS and RS. And in order to produce that channel sequence you must specify : "channelmap=0|1|4|5|2|3:5.1(side)".

I think Kodi AC-4 is incorrectly invoking FFMPEG with "channelmap=0|1|2|3|4|5:5.1(side)", which swaps the final two pairs of channels.

It can easily be seen visually. When Kodi is set to "pass-through" to send its decoded output to the external audio system via HDMI, here is what is shown for the AC-3 version of 5.1 out of Kodi AC-4 (on the left) and AC-4 version out of Kodi AC-4 (on the right):

      


Looking at it from the perspective of the Windows PC itself (on which Kodi AC-4 is running), when the audio output is instead directed through DirectSound to the 5.1 speakers attached to the PC it looks like this. Again, AC-3 on the left and AC-4 on the right.

     

NOTE: there is an accidental unintended attachment to this post. I've tried to delete it but the forum software refuses to delete is when I push"update post". It's just stuck. Please disregard that attachment (or, if a Moderator could remove it I'd appreciate it). Sorry for the distraction.

The version of ffmpeg that I used has the same channel mapping for AC-4 as is being used by AC-3 so I believe there's either a mapping issue within Kodi or your local broadcaster(s) have some channels out of sequence which is also highly probable.  Just getting the video in sync with the audio in the Phoenix area took months to resolve because the local broadcasters were using incorrect timestamps on their video streams.  I don't have the time to address any issues with Kodi for a while as I have a day job that keeps me busy.

[ferrels]

I am glad it works for you but the @ferrels Kodi branch I read about apparently was based on an older version of Nexus that spams the server.  Version 20.2.1 of  pvr.nextpvr is highly recommended and earlier versions for Nexus are not supported.

When producing Kodi builds I suggest it would be wise to target Matrix or if possible create nightly for Nexus.  There are exciting things coming often now.

Martin

I took your advice and created a Matrix build (ver. 19.3) from github.  It seems to be working just fine and has none of the problems with missing add-ons repositories.

HEVC/AC-4 programming seems to work just fine but I only have a Dolby 2.1 surround sound system so I can't test the other surround sound configurations.

Here's a download link to the installer for folks who want to try it:  Kodi-Matrix-AC4-setup.exe

[ferrels]

In passing, I believe I've discovered a problem with Kodi AC-4 as far as the sequence of channels in the AC-4 FFMPEG-decoded output. I was doing a complete matrix of tests tonight, using all available client apps on all available platforms (that I have available to me), documenting the type audio output (if any) and whether it was 2.0, 5.1, or faux-5.1 (i.e. the SD version).

There is a thread on the SD forum discussing copying ATSC 3.0 MPG/TS recordings containing imbedded AC-4 5.1 and replacing it in the output with transcoded AC-3 5.1. In that discussion there was the topic of the ChannelMap operand for FFMPEG. The correct sequence of channels expected by all external hardware and AVR's is 5.1 is L, R, C, LFE (SW), LS and RS. And in order to produce that channel sequence you must specify : "channelmap=0|1|4|5|2|3:5.1(side)".

I think Kodi AC-4 is incorrectly invoking FFMPEG with "channelmap=0|1|2|3|4|5:5.1(side)", which swaps the final two pairs of channels.

It can easily be seen visually. When Kodi is set to "pass-through" to send its decoded output to the external audio system via HDMI, here is what is shown for the AC-3 version of 5.1 out of Kodi AC-4 (on the left) and AC-4 version out of Kodi AC-4 (on the right):

      


Looking at it from the perspective of the Windows PC itself (on which Kodi AC-4 is running), when the audio output is instead directed through DirectSound to the 5.1 speakers attached to the PC it looks like this. Again, AC-3 on the left and AC-4 on the right.

     

NOTE: there is an accidental unintended attachment to this post. I've tried to delete it but the forum software refuses to delete is when I push"update post". It's just stuck. Please disregard that attachment (or, if a Moderator could remove it I'd appreciate it). Sorry for the distraction.

The version of ffmpeg that I used has the same channel mapping for AC-4 as is being used by AC-3 so I believe there's either a mapping issue within Kodi or your local broadcaster(s) have some channels out of sequence which is also highly probable.  Just getting the video in sync with the audio in the Phoenix area took months to resolve because the local broadcasters were using incorrect timestamps on their video streams.  

Ffmpeg officially only supports Dolby AC-3 audio which specifies up to 6 channels.  So anything beyond Dolby 5.1 gets treated as if it's 5.1 audio.  A look at channel_layout.h in the lavutil portion of the ffmeg library confirms this with the following channel mapping:


#define AV_CH_LAYOUT_7POINT0                     (AV_CH_LAYOUT_5POINT0|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT)
#define AV_CH_LAYOUT_7POINT0_FRONT         (AV_CH_LAYOUT_5POINT0|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER)
#define AV_CH_LAYOUT_7POINT1                     (AV_CH_LAYOUT_5POINT1|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT)
#define AV_CH_LAYOUT_7POINT1_WIDE           (AV_CH_LAYOUT_5POINT1|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER)
#define AV_CH_LAYOUT_7POINT1_WIDE_BACK  (AV_CH_LAYOUT_5POINT1_BACK|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER)


Also see: https://trac.ffmpeg.org/ticket/3595
and
https://ffmpeg-user.ffmpeg.narkive.com/j...io-support
and
https://forum.videohelp.com/threads/4001...ing-FFmpeg