vdr December 2024

vdr@linuxtv.org

3 participants
2 discussions

Identifying MPEG-4 HE-AAC (LATM, LAOS) audio formats
by Marko Mäkelä 30 Dec '24

30 Dec '24

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. The step was to introduce a second free-to-air DVB-T2 bouquet to carry some channels that were previously only available with DVB-T and MPEG-2. 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.) Unlike our first free-to-air DVB-T2 bouquet, which uses MPEG-4 H.264 video with AC3 audio, the second one uses H.264 video and HE-AAC audio, also known as LATM or LOAS. This had to be explicitly enabled for my output device: https://github.com/reufer/rpihddevice/issues/20 The HE-AAC support in rpihddevice is experimental, maybe because the sampling rate is hard-coded as 48 kHz and the number of channels as 2. Unlike AC3, it does not look like these parameters would be available in any audio frame header. As far I understood from a NorDig.org specification, the sampling rate would always be 48 kHz, but the number of channels could be identified by something in the container, specifically, Table 12.28 and Table 12.29 at page 164 of https://nordig.org/wp-content/uploads/2016/03/NorDig-Unified-Requirements-v… What would have to be changed in VDR or rpihddevice or both to correctly switch between 2-channel and 5.1-channel HE-AAC audio? This is mostly an academic question and exercise, because I only have stereo audio hardware and don't know if any programming is actually available with multichannel audio. Best regards, Marko

3 7

Using vdr-dpg package for bug hunting?
by schorpp 06 Dec '24

06 Dec '24

Hello, I'm about fixing this old BUG exiting VDR on every 1st recording start: # gdb attach <pid of vdr> Program received signal SIGFPE, Arithmetic exception. [Switching to Thread 0x9c801b40 (LWP 8182)] 0x08136f6a in cFrameDetector::Analyze(unsigned char const*, int) () (gdb) bt #0 0x08136f6a in cFrameDetector::Analyze(unsigned char const*, int) () #1 0x081295b2 in cRecorder::Action() () #2 0x08165e13 in cThread::StartThread(cThread*) () #3 0xb7693d97 in start_thread () from /lib/i386-linux-gnu/libpthread.so.0 #4 0xb73addfe in clone () from /lib/i386-linux-gnu/libc.so.6 (gdb) bt full #0 0x08136f6a in cFrameDetector::Analyze(unsigned char const*, int) () No symbol table info available. #1 0x081295b2 in cRecorder::Action() () No symbol table info available. #2 0x08165e13 in cThread::StartThread(cThread*) () No symbol table info available. #3 0xb7693d97 in start_thread () from /lib/i386-linux-gnu/libpthread.so.0 No symbol table info available. #4 0xb73addfe in clone () from /lib/i386-linux-gnu/libc.so.6 No symbol table info available. I've installed the vdr-dbg debian package to provide debugging symbols to vdr gdb bt full but there's no README included how to use it. # dpkg -L vdr-dbg /. /etc /etc/init /etc/init/vdr-dbg.conf ?* /etc/init/vdr-exit-other.override ?* /usr /usr/lib /usr/lib/debug /usr/lib/debug/.build-id /usr/lib/debug/.build-id/10 /usr/lib/debug/.build-id/10/e8b576883246ca77ad6f40e2c26053ba2d357c.debug /usr/lib/debug/.build-id/86 /usr/lib/debug/.build-id/86/d9bba0c546ad5d7429259292b259103aabba03.debug /usr/lib/debug/.build-id/6d /usr/lib/debug/.build-id/6d/6631fca1b8d4962b2725add0c729fdeba6aa40.debug /usr/share /usr/share/doc /usr/share/doc/vdr-dbg /usr/share/doc/vdr-dbg/copyright /usr/share/doc/vdr-dbg/changelog.Debian.gz /usr/share/doc/vdr-dbg/changelog.gz /usr/bin /usr/bin/vdr-dbg *Does this package interfere with my production vdr installation? Can I just replace /usr/bin/vdr with /usr/bin/vdr-dbg in runvdr script? There's only a gdb beginners guide in the wiki: http://www.vdr-wiki.de/wiki/index.php/Gdb http://www.vdr-wiki.de/wiki/index.php?title=Spezial%3ASuche&search=vdr-dbg&… ? Y tom

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vdr December 2024