Download helper doesn't download HLS audio at all and m2ts incorrectly

[Roy]

Hi

I am using Video DownloadHelper 7.1.3a5 and companion app 1.1.3 for firefox on windows 7 64 bit.

I am trying to download an audio file. The download seems fine until it reaches 99% (see picture attached). There it freezes and after a while it reports error: MP2T - No data received. This is the details it reports about the error:

MP2T - No data received

moz-extension://902451b1-f5fc-4bf7-b14a-05d52dee9712/background/main.js:1
value@moz-extension://902451b1-f5fc-4bf7-b14a-05d52dee9712/background/main.js:1:200466
value@moz-extension://902451b1-f5fc-4bf7-b14a-05d52dee9712/background/main.js:1:165049
value@moz-extension://902451b1-f5fc-4bf7-b14a-05d52dee9712/background/main.js:1:111973
value/</e.endTimer<@moz-extension://902451b1-f5fc-4bf7-b14a-05d52dee9712/background/main.js:1:164199

I have tried several other recordings from the same web site, and they are all the same. When I check the checkbox for HLS as M2TS it downloads till 100% and creates an m2ts file. But when I play the file in VLC I can hear distortions in the audio. I use VLC version 2.2.2, which is quite old, but I don't think that VLC is causing the audio distortion. Is this because of a bug in DownloadHelper or a bug on the site I'm downloading from?

The audio comes from an old historical recording:
https://www.nb.no/nbsok/nb/86dd69abd456ddbeab7817a70ad623fd?index=4

Can anyone offer some insight as to what I can do? I have found that the distortions are now alwayd in the same place. Sometimes there are many of them, and other times there are few. I have attached one of my attempts at downloading, and during the first couple of minutes there are quite a few spots where the audio seems scrambled.

https://drive.google.com/file/d/1B9m8Dhq2EdqJLfCI4BDEsGaODKIdz-ld/view?usp=sharing

[mig]

Thanks for the clear reporting. I gave it a try and i confirm the problem.

What happens here is that this site is using an MPEG-2 encoded audio stream. This is in the standards, but i did not develop the code to handle this format in the HLS module. The reason is that after 3 years supporting HLS, this is the first time i see a case of audio not being encoded in aac.

To be honest, given how seldom this HLS encoding is, developing the appropriate code shows very low in the TODO list.

Using "HLS as M2TS" was a good idea (in this case the add-on code does not try to interpret the audio data and store the downloaded bytes with far less adjustments). But, as it is often the case when doing this, there might be some timing issues. Did you try converting the resulting distorted audio file ? Sometimes converters can fix those things.
 

[Roy]

Thanks for your quick reply.

I have downloaded the m2ts file, and tried converting it with ffmpeg, both with -acodec copy and -acodec mp3 options, the distortions are still there. When converting to mp3, ffmpeg reported

[mp3 @ 003f78c0] overread, skip -6 enddists: -4 -4
[mp3 @ 003f78c0] overread, skip -7 enddists: -4 -4
    Last message repeated 1 times
[mp3 @ 003f78c0] overread, skip -7 enddists: -5 -5ts/s
[mp3 @ 003f78c0] overread, skip -8 enddists: -5 -5
[mp3 @ 003f78c0] overread, skip -5 enddists: -3 -3ts/s
[mp3 @ 003f78c0] overread, skip -5 enddists: -3 -3ts/s
[mp3 @ 003f78c0] overread, skip -6 enddists: -1 -1ts/s
[mp3 @ 003f78c0] overread, skip -7 enddists: -1 -1ts/s
[mp3 @ 003f78c0] overread, skip -7 enddists: -4 -4ts/s
[mp3 @ 003f78c0] overread, skip -6 enddists: -3 -3
    Last message repeated 1 times
[mp3 @ 003f78c0] overread, skip -6 enddists: -4 -4ts/s
[mp3 @ 003f78c0] overread, skip -6 enddists: -2 -2ts/s
[mp3 @ 003f78c0] overread, skip -7 enddists: -5 -5
[mp3 @ 003f78c0] overread, skip -5 enddists: -4 -4
[mp3 @ 003f78c0] overread, skip -6 enddists: -5 -5ts/s
[mp3 @ 003f78c0] overread, skip -5 enddists: -1 -1
[mp3 @ 003f78c0] overread, skip -6 enddists: -1 -1ts/s
[mp3 @ 003f78c0] overread, skip -5 enddists: -1 -1
[mp3 @ 003f78c0] overread, skip -6 enddists: -4 -4ts/s
[mp3 @ 003f78c0] overread, skip -7 enddists: -6 -6ts/s
[mp3 @ 003f78c0] overread, skip -5 enddists: -4 -4ts/s
[mp3 @ 003f78c0] overread, skip -7 enddists: -6 -6
[mp3 @ 003f78c0] overread, skip -7 enddists: -4 -4
[mp3 @ 003f78c0] overread, skip -6 enddists: -5 -5
[mp3 @ 003f78c0] overread, skip -6 enddists: -4 -4ts/s
[mp3 @ 003f78c0] overread, skip -7 enddists: -4 -4
[mp3 @ 003f78c0] overread, skip -7 enddists: -2 -2ts/s
[mp3 @ 003f78c0] overread, skip -6 enddists: -2 -2ts/s
[mp3 @ 003f78c0] overread, skip -6 enddists: -4 -4ts/s
[mp3 @ 003f78c0] overread, skip -7 enddists: -5 -5ts/s
[mp3 @ 003f78c0] overread, skip -7 enddists: -4 -4
[mp3 @ 003f78c0] overread, skip -7 enddists: -3 -3ts/s
[mp3 @ 003f78c0] overread, skip -5 enddists: -2 -2ts/s
[mp3 @ 003f78c0] overread, skip -5 enddists: -1 -1ts/s
size=    8260kB time=00:46:57.02 bitrate=  24.0kbits/s

The distorted spots vary from download to download, so it seems they are ocurring randomly. I think you are right in guessing that timing issues are causing this. Do you have suggestions as to other solutions to rip this type of streams?

[mig]

Since you have everything in place, it might be worth trying with "-acodec aac", "-acodec ac3", "-acodec adpcm_g722", "-acodec adpcm_ima_wav", "-acodec amr_nb", "-acodec amr_wb", ... (use "ffmpeg -codecs" and search for "EA" for available audio encoders).

If this does not work, i'm afraid i have no solution for this.

[Roy]

I tried converting the file that Video Download helper downloaded, and the audio distortions are still there. So the distortions comes while downloading or merging the finished TS-file.

Could you elaborate a bit on how Video Download Helper treats a chunked audio stream while downloading it in HLS-as-M2TS-mode? I guess that the distortions comes when the chunks are merged together into one file, as TS-format:

https://stackoverflow.com/questions/11962998/mpeg-2-ts-video-audio-skipping-http-live-streaming

[mig]

The HLS-as-M2TS-mode is quite basic: it concatenates downloaded chunks into a single file. There is no treatment that could affect (in good or bad) the timing information.