No audio heard via UDP to VLC questions please.

[Basil]

I tried a 1MS transmission from my Pluto last night and although my Minitiouner could decode the audio and I heard it fine, as did others using Minitioune, if i streamed it via UDP from the Minitioune software to my VLC programme there was no audio. I tried a different video to transmit and that then produced audio both on the Minitioune software and via UDP to VLC.

What might I investigate to find a fix please, so all videos will have decodable audio in Minitioune and VLC? Thanks. Chris 2E0ILY

[g0mjw]

This could be many things. There isn't sufficient information to be sure, though the Pluto isn't great at higher bit rates and in any case why would someone want to use 1 Ms when 333ks is usually good enough and used 1/3rd of the spectrum and 1/3rd of the power.

To diagnose can you say how you are generating the transport stream, e.g. with a Portsdown or DATVEasy or a script, with what audio codecs, what is the FEC, which Pluto firmware etc etc. It could be overruns, or incorrect PIDs or an incompatible codec, or too fast for the pluto or...

The fact that a different video worked and another didn't seems to point to the video complexity being too high for the encoder and buffers overflowing. If that is the case you need to dial back the parameters in your script or program that generates the Transport stream. This can also be caused by setting the wrong FEC and trying to squeeze more down the channel that will fit.

Mike

[G4EWJ]

I recall a similar case recently of odd audio behaviour. Try looking at and selecting different options in VLC. Right click on the VLC window and then select AUDIO / STEREO MODE. Also look at AUDIO TRACK and AUDIO DEVICE.

Brian
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vlcaudio1.png (137.91 KiB) Viewed 3311 times

[G4EWJ]

I'm watching your transmission of the woman dancing and sometimes there's audio and sometimes there isn't. Is that expected? I tried all the VLC stereo settings, but it didn't change anything.

Brian

[Basil]

Hi Brian, no, the TX settings didn't change all the time I was trying 1MS rate.

I fiddled with the VLC Preferences - Tools - Input / Codecs - Hardware Accelerated Decoding options and I too would spasmodically receive audio, but it seemed pretty random. Thanks for listening though, not sure what to check now, 500Ks works fine.

[g0mjw]

I asked earlier but will ask again. What is the transport stream rate? What is the video bit rate, what is the audio codec, what is the FEC?

Mike

[Basil]

Hello Mike, here's the info, or as much as I am able to ID as to what you need, thanks.


FEC used is 2-3 using QPSK


This is from a screen grab of the batch file for 1MS running:

libavfilter 7. 85.100 / 7. 85.100
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
libpostproc 55. 7.100 / 55. 7.100
[swscaler @ 0000021bbcc4b400] Warning: data is not aligned! This can lead to a speed loss
Input #0, dshow, from 'video=OBS-Camera':
Duration: N/A, start: 169069.080000, bitrate: N/A
Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1080, 25 fps, 25 tbr, 10000k tbn, 10000k tbc
Guessed Channel Layout for Input Stream #1.0 : stereo
Input #1, dshow, from 'audio=OBS-Audio':
Duration: N/A, start: 169069.183000, bitrate: 1411 kb/s
Stream #1:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo (native) -> hevc (hevc_nvenc))
Stream #1:0 -> #0:1 (pcm_s16le (native) -> aac (native))
Press [q] to stop, [?] for help
Output #0, mpegts, to 'udp://192.168.178.20:8282?pkt_size=1316':
Metadata:
service_provider: Chris 2E0ILY
service_name : DATV
encoder : Lavf58.45.100
Stream #0:0: Video: hevc (hevc_nvenc) (Main), yuv420p(progressive), 1920x1080, q=-1--1, 1088 kb/s, 25 fps, 90k tbn, 25 tbc
Metadata:
encoder : Lavc58.91.100 hevc_nvenc
Side data:
cpb: bitrate max/min/avg: 0/0/1088000 buffer size: 2176000 vbv_delay: N/A
Stream #0:1: Audio: aac (LC), 48000 Hz, stereo, fltp, 64 kb/s
Metadata:
encoder : Lavc58.91.100 aac
frame= 3305 fps= 25 q=31.0 size= 21278kB time=00:02:11.62 bitrate=1324.2kbits/s speed=0.996x



Does this cover all you need to hopefully advise? I can link to one of the videos that gives the issue if you like? Thanks.

Pluto is running 0303 and is out by the dish on the LAN using a powered hub at the Pluto.

[g0mjw]

I see you are right at the maximum bit rate, I would drop it a little, say to 1.3 Mb/s. You have 25fps full HD, with a CBR of 1088 and it looks like 64kbs audio. I assume this is developed by a script. For the same TS rate I was using something like this. You will need to change the frame rate to 25 but what else is different and does it have the same issue?

c:\ffmpeg\bin\ffmpeg -f dshow -i video="OBS-Camera" -thread_queue_size 512 -f dshow -i audio="OBS-Audio" -vcodec hevc_nvenc -s 1920x1080 -bf 0 -pix_fmt yuv420p -b:v 1100k -r 30 -preset slow -profile:v main -rc cbr_hq -rc-lookahead 5 -acodec aac -aac_coder twoloop -ar 48000 -ac 1 -b:a 64k -f mpegts -muxrate 1300k -streamid 0:256 -streamid 1:257 -max_delay 2500000 -pcr_period 40 -pat_period 0.4 "udp://192.168.1.46:8282?pkt_size=1316"

[Basil]

Thanks Mie and all who replied, I'll compare scripts but being well outside my comfort zone I am doubtful of resolving this, I can but try though.