Issues with AAC 5.1 using German DVB-T2

backslash · September 3, 2017 at 4:55 PM

I am facing a strange issue with AAC 5.1 here in Germany using latest LE and Tvheadend for watching DVB-T2. While watching live tv with AAC 5.1 audio I have no issues but if I try to watch a recording (e.g. of the same programe) which includes AAC 5.1 audio I am facing annoying audio hick-ups. Is Kodi relying on differtent audio decoders for live tv and recordings? This is pretty annoying because any recording which includes AAC 5.1 audio is sadly unwatchable. I started using Kodi with Krypton and the DVB-T2 release here in Germany and was facing the issue independent of LE and Kodi Krypton version. I installed 8.1.1 beta recently from scratch and the issue remains. Any ideas?

noggin · September 5, 2017 at 9:01 AM

Quote from backslash

I am facing a strange issue with AAC 5.1 here in Germany using latest LE and Tvheadend for watching DVB-T2. While watching live tv with AAC 5.1 audio I have no issues but if I try to watch a recording (e.g. of the same programe) which includes AAC 5.1 audio I am facing annoying audio hick-ups. Is Kodi relying on differtent audio decoders for live tv and recordings? This is pretty annoying because any recording which includes AAC 5.1 audio is sadly unwatchable. I started using Kodi with Krypton and the DVB-T2 release here in Germany and was facing the issue independent of LE and Kodi Krypton version. I installed 8.1.1 beta recently from scratch and the issue remains. Any ideas?

The UK has been using AAC 5.1 for a while on DVB-T2 (we're AC3 on satellite but AAC on terrestrial) and I've not noticed any issues with playback (though there have been some 5.1 -> 2.0 mix down issues where I don't think AAC mix-down metadata is followed as well as AC3).

I'll check a recording of a BBC One HD 5.1 drama I made over the weekend with various LibreElec installs - as I have it in both AAC 5.1 (from T2) and AC3 5.1 (from S2).

I'd heard Germany was using E-AC3 on DVB-T2 (as France does on DVB-T for HD) - is there a split between broadcaster?

ALSO - have you tried watching the file outside of the PVR sub-system (i.e. playing it from Videos by mounting your Recorded TV folder as a source in Videos->Files or copying it to a location available to Videos->Files?)

backslash · September 5, 2017 at 9:57 AM

If I watch the recordings using VLC they play just fine. It's just that if I watch the recordings using Kodi that I have this annoying audio hick-ups. I can watch 4K Material and anything else that I throw at my box without any issues. It's just the damn recordings which include AAC 5.1 that are causing issues.

The audio encoding depends on the channel. Some channels like Arte use AAC 5.1 while other channels use something else for audio.

noggin · September 5, 2017 at 5:50 PM

OK - checked some 5.1 stuff from BBC One HD in the UK.

This is from last Sunday's episode of Cormoran Strike - both DVB-T2 AAC 5.1 and DVB-S2 AC3 5.1

Both play as files and from within the TV Headend PVR client with no problems on my Haswell Celeron Chromebox running LibreElec 8.0.2. I'm configured for 5.1 output over HDMI and my amp is being sent 5.1 PCM with the AAC clip and bitstreamed AC3 for the AC3 clip. I have no audio glitching.

My AAC 5.1 BBC One HD recording has the following properties from Media Info (I've snipped the filename, and the EPG EIT stuff from the bottom) BBC HD stuff carries either a 2.0 or 5.1 AAC main programme channel, and then a mono additional audio description channel (for people with visual impairment to audibly describe visual action) which receivers add to the main programme sound feed.

(You'll also note the video is flagged progressive. This is because UK H264 HD encoders on DVB-T2 switch between i25 and p25 encoding on-the-fly. The Media Info is actually for a short clip I created using 'dd' to crop the first 500MB of the file, as the recording started early and started with the end of a 2.0 AAC show)

Code

Format                                   : MPEG-TS
File size                                : 200 MiB
Duration                                 : 6mn 46s
Overall bit rate mode                    : Variable
Overall bit rate                         : 4 130 Kbps

Video
ID                                       : 6601 (0x19C9)
Menu ID                                  : 17540 (0x4484)
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 4 frames
Codec ID                                 : 27
Duration                                 : 6mn 45s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 25.000 fps
Standard                                 : Component
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Audio #1
ID                                       : 6602 (0x19CA)
Menu ID                                  : 17540 (0x4484)
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Muxing mode                              : LATM
Codec ID                                 : 17
Duration                                 : 6mn 46s
Bit rate mode                            : Variable
Channel(s)                               : 6 channels
Channel positions                        : Front: L C R, Side: L R, LFE
Sampling rate                            : 48.0 KHz
Frame rate                               : 46.875 fps (1024 SPF)
Compression mode                         : Lossy
Delay relative to video                  : -806ms
Language                                 : English

Audio #2
ID                                       : 6606 (0x19CE)
Menu ID                                  : 17540 (0x4484)
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : HE-AAC / LC
Muxing mode                              : LATM
Codec ID                                 : 17
Duration                                 : 6mn 45s
Bit rate mode                            : Variable
Channel(s)                               : 1 channel
Channel positions                        : Front: C
Sampling rate                            : 48.0 KHz / 24.0 KHz
Frame rate                               : 23.438 fps (1024 SPF)
Compression mode                         : Lossy
Delay relative to video                  : -611ms
Language                                 : English
Language, more info                      : Visual impaired commentary

Text
ID                                       : 6605 (0x19CD)
Menu ID                                  : 17540 (0x4484)
Format                                   : DVB Subtitle
Codec ID                                 : 6
Duration                                 : 6mn 44s
Delay relative to video                  : 2s 261ms
Language                                 : English

Menu
ID                                       : 6600 (0x19C8)
Menu ID                                  : 17540 (0x4484)
Duration                                 : 6mn 46s
List                                     : 6601 (0x19C9) (AVC) / 6602 (0x19CA) (AAC, English) / 6606 (0x19CE) (AAC, English) / 6605 (0x19CD) (DVB Subtitle, English)
Language                                 :  / English / English / English
Service name                             : BBC ONE HD
Service type                             : advanced codec HD digital television

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