* Re: [vdr] Re: Identifying MPEG-4 HE-AAC (LATM, LAOS) audio formats
2024-12-06 21:31 ` [vdr] Identifying MPEG-4 HE-AAC (LATM, LAOS) audio formats schorpp
@ 2024-12-09 17:23 ` Marko Mäkelä
0 siblings, 0 replies; 2+ messages in thread
From: Marko Mäkelä @ 2024-12-09 17:23 UTC (permalink / raw)
To: VDR Mailing List; +Cc: alsa-devel
Fri, Dec 06, 2024 at 10:31:06PM +0100, schorpp wrote:
>Am 06.12.24 um 21:32 schrieb Marko Mäkelä:
>>A couple of weeks ago, Finland took the penultimate step to get rid
>>of DVB-T. Since years, we had DVB-T and DVB-T2 running in parallel.
>>The DVB-T transponders should be shut down in 2025.
>
>same here but h.265 video and aac audio.
Right, it's H.265 video in Germany. I found somewhere a reference to
something that would transcode H.265 into H.264 on the fly on a
Raspberry Pi 3, so that the Videocore GPU could play it in real time.
>>The VDR channel search failed to find this transponder; I ran a
>>patched version of https://github.com/mighty-p/t2scan/pull/15/ to
>>generate a new channels.conf. (Is this a bug of VDR, or a feature? I
>>remember that when I originally set up VDR, I had to get a
>>channels.conf from tscan or t2scan.)
>
>have You tried the latest git version of scan in dvb-utils
>@linuxtx.org repo?
At https://git.linuxtv.org/v4l-utils.git I found a reference to the
command dvbv5-scan. An "apt search dvbv5-scan" on my Debian Sid as well
as on Raspbian 12.8 yielded two packages: dvb-tools and w-scan-cpp. I
vaguely remember that I had used the latter one a few years ago. I just
invoked the following on the Raspberry Pi:
w_scan_cpp -c FI
The output during scanning looks convincing, but the program seems to
get stuck waiting for something at the end, for several minutes.
I also tried to invoke dvbv5-scan from dvb-tools, but it seems to
require a file that contains some initial parameters.
Anyway, I was mainly wondering if it is normal that the EPG update in
VDR did not find the new transponder. I guess it is; the search space
would be huge if it had to cover satellite, cable, terrestrial and some
IPTV sources as well.
>>The HE-AAC support in rpihddevice is experimental,
>
>as it has been in ffmpeg until today and rpihddevive is based on it?
As in:
#ifdef ENABLE_AAC_LATM
#warning "experimental AAC-LATM frame parser enabled, only 2ch/48kHz supported!"
#endif
>Have You tried the latest git ffprobe version, does it detect the aac
>flavor of Your dvb-t2 DVB channels correctly?
I only have 2-channel recordings or DVB-T2 streams available to me.
Those already play without any problems. But I don't have any recording
with multichannel audio. I would like to implement correct detection and
playback of multichannel HE-AAC audio, so that the AAC audio support
could be enabled by default in rpihddevice.
>Have You tried latest git mediainfo?
I was reading the libmediainfo source code a few days ago. I guess I
should just have executed mediainfo on an MPEG-4 TS file inside a
debugger, to find out how and where exactly it detects the audio
parameters.
>Not at all academic. Since AVRs do not implement Fraunhofer codecs we
>need a HDNI PCM Multichannel driver for the raspberry pi to playback
>5.1 channel aac without transcoding it to ac3 which can be done with
>mplayer on the fly.
Right, also according to the NorDig specification, some transcoding of
audio is mandatory for some audio output options.
>I've made a HDMI PCM Multichannel output to AVR driver patch for the
>Allwinner SoC alsa audio driver, look for it on the alsa-dev list
>archives.
Sorry, I could not find it. I figured out that AVR here must refer to
Audio Video Receiver. The only HDMI output devices that I have are
displays with 2 built-in speakers. I believe that I am currently using
2-channel PCM audio output.
Are there any sample MPEG TS recordings with 5.1 channel AAC audio?
That would be very helpful. In a 2-channel setup, would it be customary
to pass through only the first 2 channels and ignore the rest?
Marko
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