[mythtv-users] corrupt audio with time stretch and SPDIF passthrough

Andrew mythtv at heathsworld.com
Thu Mar 11 14:42:48 UTC 2010


On Wed, Mar 10, 2010 at 11:01 AM, Andrew <mythtv at heathsworld.com> wrote:

> On Mon, Mar 8, 2010 at 8:38 PM, Andrew <mythtv at heathsworld.com> wrote:
>
>> On Mon, Mar 8, 2010 at 4:43 PM, Jean-Yves Avenard <jyavenard at gmail.com>wrote:
>>
>>> Hi
>>>
>>> On 8 March 2010 17:29, Nick Rout <nick.rout at gmail.com> wrote:
>>> >
>>> > It is certainly possible to use time stretch with spdif out. However
>>> > my recordings are not ac3 or dts, it's 2 channel mp2 (from a dvb-s
>>> > recording).
>>>
>>> With 0.22 ; timestrech is only possible on PCM stream ; basically
>>> whenever Myth is doing the audio decoding (as it is the case with your
>>> mp2 stream).
>>>
>>> 0.23 has a complete rewrite of that part; and you will be able to
>>> timestretch any materials.
>>>
>>> Myth will decode AC3 / DTS internally, apply the timestretch then
>>> re-encode it as AC3.
>>>
>>> Same thing apply with the volume control ; you'll be able to change
>>> the audio volume directly from myth for digital audio content (using
>>> the "software" mixer.
>>>
>>> Jean-Yves
>>>
>>>
>> That is fantastic news!  Thanks for the great discussion.
>>
>
> This fixed the problem, thanks!  I do have another issue that has come up
> since and that is mythmusic has no audio when playing .mp3's.  Shouldn't
> mythmusic use those same audio output settings for digital SPDIF and just
> work? They are local mp3's.
>
>
It's an issue with ALSA...  A simple restart of alsa-utils fixes the audio.
Moving between different recordings doesn't seem to bork it, however
mythmusic will not play audio 50% of the time i start it.  When it doesn't
play audio and I go back to a TV show the audio doesn't work either (alsa
must have died).  It's like it kills alsa and it wont work properly again
until a restart of alsa is done.  Another interesting thing is that when
going into mythmusic when the audio is broken, I can let it play silence and
restart the service in a terminal.  Doing this the audio starts up and plays
fine.  There must be something that crashes alsa when first entering into
the mythmusic screen...  I suppose this is a new bug introduced that
hopefully is fixed soon.

@myth:~$ mythfrontend --version
xprop:  unable to open display 'localhost:11.0'
Please include all output in bug reports.
MythTV Version   : 23670
MythTV Branch    : branches/release-0-22-fixes
Network Protocol : 50
Library API      : 0.22.20091023-1
QT Version       : 4.5.2
Options compiled in:
 linux debug using_oss using_alsa using_pulse using_jack using_backend
using_dvb using_firewire using_frontend using_glx_proc_addr_arb
using_hdhomerun using_hdpvr using_iptv using_ivtv using_joystick_menu
using_libfftw3 using_lirc using_mheg using_opengl_video using_opengl_vsync
using_qtwebkit using_v4l using_x11 using_xrandr using_xv using_xvmc
using_xvmc_vld using_xvmcw using_bindings_perl using_bindings_python
using_opengl using_vdpau using_ffmpeg_threads using_libavc_5_3 using_live
using_mheg
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