audiomixer output is delayed silence when 2nd sink pad is added

[Nicolas Dufresne]

Hi,

Le vendredi 23 décembre 2022 à 20:55 +0530, Pradeep Acharya via gstreamer-devel
a écrit :
> Hi,
> 
> I;m using audiomixer element to mix audio from live sources in a video
> conference call. The o/p of audio mixer is given to the opus encoder and then
> transmitted to the remote end . It works fine when there is only one one sink
> pad attached to the mixer i,,e only one client joins the conference. Problem
> starts when the 2nd participant joins and a second sink pad is added to the
> mixer.
> 
> I observe a delay proportional to the time the first user joined. After some
> time, the mixer starts to output data. Audio is not lost but delayed and the
> delay continues. I tried some of the configuration parameters like " start-
> time-selection" to 1 and "start-time" to 0. , "ignore-inactive-pads" to TRUE.
> There is no improvement even after configuring these params. From gstreamer
> logs, i could see that

somehow gives me the impression this is the same issue that led into adding the
"min-upstream-latency" property. When you add pad, the latency changes, and that
can disturb the playback, using   upstream-latency you can fix that latency so
your worst case ahead of time.  Let's hope this is it.

regards,
Nicolas

> 
> 0:00:39.011285060 ^[[32m3313765^[[00m 0x7f6fdc00e460 ^[[37mDEBUG  ^[[00m
> ^[[00;35m          aggregator
> gstaggregator.c:2172:gst_aggregator_query_latency_unlocked:<audiomixer_111>^[[
> 00m configured latency live:true min:20000000 max:20000000  ---> when first
> sink pad is added 
> 
> 0:00:39.022481190 ^[[32m3313765^[[00m 0x7f7068024760 ^[[33;01mLOG    ^[[00m
> ^[[00;35m          aggregator
> gstaggregator.c:3415:gst_aggregator_pad_buffer_consumed:<audiomixer_111:sink_0
> >^[[00m Signaling buffer consumed from thread 0x7f7068024760
> 0:00:39.022543769 ^[[32m3313765^[[00m 0x7f7068024760 ^[[37mDEBUG  ^[[00m
> ^[[00;35m          aggregator
> gstaggregator.c:3513:gst_aggregator_pad_pop_buffer:<audiomixer_111:sink_0>^[[0
> 0m Consumed: buffer: 0x7f6fa0004120, pts 0:00:00.822554913, dts
> 0:00:37.845570590, dur 0:00:00.020000000, size 3840, offset none, offset_end
> none, flags 0x0
> 
> 0:00:39.023672822 ^[[32m3313765^[[00m 0x7f7068024760 ^[[37mTRACE  ^[[00m
> ^[[00;35m          aggregator
> gstaggregator.c:3446:gst_aggregator_pad_clip_buffer_unlocked:<audiomixer_111:s
> ink_0>^[[00m Clipping: buffer: 0x7f6fa0004240, pts 0:00:00.842553968, dts
> 0:00:37.847505654, dur 0:00:00.020000000, size 3840, offset none, offset_end
> none, flags 0x800
> 
> 0:00:39.023926552 ^[[32m3313765^[[00m 0x7f7068024760 ^[[37mTRACE  ^[[00m
> ^[[00;35m          aggregator
> gstaggregator.c:713:gst_aggregator_default_finish_buffer:<audiomixer_111>^[[00
> m GstAggregator: 0x7f70680562a0 pushing buffer buffer: 0x7f6ff4064900, pts
> 0:00:00.842541666, dts 99:99:99.999999999, dur 0:00:00.020000000, size 3840,
> offset 40442, offset_end 41402, flags 0x800
> 
> 
> When 2nd participant joins after 8 minutes, sink_1 pad is created for
> audiomixer.  Audio o/p is delayed by ~ 38 seconds i,,e time duration of  1st
> sink pad's (sink_0 ) buffer start time .
> 
> 0:08:53.918540128 ^[[32m3313765^[[00m 0x7f6f98006e70 ^[[36mINFO   ^[[00m
> ^[[00;35m          aggregator
> gstaggregator.c:1524:gst_aggregator_start_srcpad_task:<audiomixer_111>^[[00m
> Starting srcpad task   ---> when second sink pad is created sink_1
> 0:08:53.918829275 ^[[32m3313765^[[00m 0x7f6fdc04a700 ^[[33;01mLOG    ^[[00m
> ^[[00;35m          aggregator
> gstaggregator.c:1380:gst_aggregator_aggregate_func:<audiomixer_111>^[[00m
> Checking aggregate
> 
> I see errors like pads not ready : no sink pads. However 2 sink pads were
> already created 
> 0:10:17.737484397 ^[[32m3313765^[[00m 0x7f7068024760 ^[[33;01mLOG    ^[[00m
> ^[[00;35m          aggregator
> gstaggregator.c:567:gst_aggregator_check_pads_ready:<audiomixer_111>^[[00m
> pads not ready: no sink pads
> 0:10:17.737527246 ^[[32m3313765^[[00m 0x7f7068024760 ^[[37mDEBUG  ^[[00m
> ^[[00;35m          aggregator
> gstaggregator.c:893:gst_aggregator_wait_and_check:<audiomixer_111>^[[00m
> possibly waiting for clock to reach 1246:02:12.632613629 (base
> 1245:51:56.050071963 start 0:10:16.562541666 latency 0:00:00.020000000 current
> 1246:02:12.613770784)
> 
> The source code works fine if i replace audio mixer element  with adder
> element  without modifying any other configurations or elements of the
> pipeline. This makes me to suspect audiomixer.  i don't see delay issues that
> i see using the audiomixer. Any suggestions on how to debug and what to look
> for ? Should i continue using adder element instead of audiomixer. 
> 
> Thanks & Regards
> Pradeep

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