[mythtv-commits] Ticket #9081: Audio choppy when bitrate not converted
MythTV
mythtv at cvs.mythtv.org
Sun Oct 10 03:13:10 UTC 2010
#9081: Audio choppy when bitrate not converted
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Reporter: paul<at>planar.id.au | Owner: jyavenard
Type: defect | Status: new
Priority: minor | Milestone: unknown
Component: MythTV - Audio Output | Version: Unspecified
Severity: medium | Keywords:
Ticket locked: 0 |
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I have an external dac - a v-dac, which is a usb audio device with burr-
brown chipset. It appears on my machine as ALSA:hw:3,0.
Since upgrading to trunk 0.24, I'm having some issues with bitrate.
When I set to ALSA:default, myth is choosing to resample my tracks from
44.1KHz to 48KHz. This sounds OK, but perhaps with a bit of audio quality
loss. If I use VLC to play the same track to ALSA:hw:3,0, the report from
/proc/asound/card3/stream0 is:
Burr-Brown from TI USB Audio DAC at usb-0000:00:1d.1-2,
full s : USB Audio
Playback:
Status: Running
Interface = 1
Altset = 1
URBs = 3 [ 8 8 8 ]
Packet Size = 192
Momentary freq = 44100 Hz (0x2c.199a)
Interface 1
Altset 1
Format: S16_LE
Channels: 2
Endpoint: 2 OUT (ADAPTIVE)
Rates: 32000, 44100, 48000
Interface 1
Altset 2
Format: S16_LE
Channels: 1
Endpoint: 2 OUT (ADAPTIVE)
Rates: 32000, 44100, 48000
If I set myth to play to ALSA:hw:3,0, it reports also that it is playing
44.1KHz, but the sound is quite choppy. It is still recognisable, but
definitely giving that "fluffy" sort of noise. The report from /proc is:
Burr-Brown from TI USB Audio DAC at usb-0000:00:1d.1-2,
full s : USB Audio
Playback:
Status: Running
Interface = 1
Altset = 1
URBs = 3 [ 8 8 8 ]
Packet Size = 192
Momentary freq = 44100 Hz (0x2c.199a)
Interface 1
Altset 1
Format: S16_LE
Channels: 2
Endpoint: 2 OUT (ADAPTIVE)
Rates: 32000, 44100, 48000
Interface 1
Altset 2
Format: S16_LE
Channels: 1
Endpoint: 2 OUT (ADAPTIVE)
Rates: 32000, 44100, 48000
I can get acceptable output by using default and allowing resampling. The
problem I have is that the DAC runs internally at 192KHz, so what I'm
doing is resampling 44.1->48->192. It seems to me that must involve some
quality loss, which I'd prefer to avoid.
I'm not sure what logs would be useful in diagnosing this. I tried
mythfrontend -v audio, and I get a log something like this.
Unfortunately, I don't think that is going to tell anyone much of
anything.
2010-10-10 14:06:58.560 Update not found (ALSA:hw:3,0)
2010-10-10 14:06:59.297 Update not found (ALSA:hw:3,0)
2010-10-10 14:07:11.606 SendReceiveStringList(REFRESH_BACKEND) called from
UI thread
2010-10-10 14:07:11.653
SendReceiveStringList(MESSAGE,CLEAR_SETTINGS_CACHE) called from UI thread
2010-10-10 14:07:11.654 Received a remote 'Clear Cache' request
2010-10-10 14:07:19.114 MythVideo::ScanVideoDirectory Scanning
(/usr/share/mythtv/server/mythvideo)
2010-10-10 14:07:27.144 XMLParse: LoadTheme using
'/usr/share/mythtv/themes/blue-abstract-wide/music-ui.xml'
2010-10-10 14:07:27.790 XMLParse, Warning: Unknown: area in repeated image
2010-10-10 14:07:27.790 XMLParse, Warning: Unknown: area in repeated image
2010-10-10 14:07:28.662 Launching: ps -ae | grep pulseaudio > /dev/null
2010-10-10 14:07:28.668 PID 16161: launched
2010-10-10 14:07:28.747 PID 16161: exited: status=256, result=1
2010-10-10 14:07:28.763 AO: SRC quality = high
2010-10-10 14:07:28.764 AO: Sample rate 32000 is supported
2010-10-10 14:07:28.764 AO: Sample rate 44100 is supported
2010-10-10 14:07:28.764 AO: Sample rate 48000 is supported
2010-10-10 14:07:28.764 AO: 1 channel(s) are supported
2010-10-10 14:07:28.764 AO: 2 channel(s) are supported
2010-10-10 14:07:28.794 AO: AC3 or DTS capable
2010-10-10 14:07:28.794 AO: 6 channel(s) are supported
2010-10-10 14:07:28.798 AO: Killing AudioOutputDSP
2010-10-10 14:07:28.798 AO: Original codec was NONE, signed 16 bit, 44
kHz, 2 channels
2010-10-10 14:07:28.798 AO: enc(0), passthru(0), canAC3(0), canDTS(0),
canLPCM(0), configured_channels(2), 2 channels supported(1)
2010-10-10 14:07:28.800 AO: Opening audio device 'hw:3,0' ch 2(2) sr 44100
sf signed 16 bit reenc 0
2010-10-10 14:07:28.800 Opening ALSA audio device 'hw:3,0'.
2010-10-10 14:07:28.800 ALSA: SetParameters(format=2, channels=2,
rate=44100, buffer_time=200000, period_time=50000)
2010-10-10 14:07:28.800 ALSA: Buffer time = 200000 us
2010-10-10 14:07:28.800 ALSA: Period time = 50000 us
2010-10-10 14:07:28.806 ALSA: Buffer size = 8820 | Period size = 2205
2010-10-10 14:07:28.810 AO: Audio fragment size: 4410
2010-10-10 14:07:28.810 AO: Audio Stretch Factor: 1
2010-10-10 14:07:28.810 AO: Ending Reconfigure()
2010-10-10 14:07:28.812 AO: kickoffOutputAudioLoop: pid = 15982
2010-10-10 14:07:28.812 AO: OutputAudioLoop: Play Event
2010-10-10 14:07:28.814 AO: Pause 1
2010-10-10 14:07:28.823 AO: OutputAudioLoop: audio paused
2010-10-10 14:07:28.875 AO: Reconfigure(): No change -> exiting
2010-10-10 14:07:28.877 avfdecoder.o: seek time 29
2010-10-10 14:07:29.029 Error seeking
2010-10-10 14:07:29.030 AO: Pause 0
2010-10-10 14:07:29.030 Read frame failed
2010-10-10 14:07:29.075 AO: OutputAudioLoop: Play Event
2010-10-10 14:07:29.246 AO: Pause 1
2010-10-10 14:07:29.275 AO: OutputAudioLoop: audio paused
2010-10-10 14:07:29.460 AO: Reconfigure(): No change -> exiting
2010-10-10 14:07:29.465 AO: Pause 0
2010-10-10 14:07:29.475 AO: OutputAudioLoop: Play Event
2010-10-10 14:07:36.596 AO: Pause 1
2010-10-10 14:07:36.625 AO: OutputAudioLoop: audio paused
2010-10-10 14:07:36.630 AO: Reconfigure(): No change -> exiting
2010-10-10 14:07:36.641 AO: Pause 0
2010-10-10 14:07:36.675 AO: OutputAudioLoop: Play Event
--
Ticket URL: <http://svn.mythtv.org/trac/ticket/9081>
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