HLS from Udemy are choppy & audio is missing words

[Peter Rihn]

Hello mig/VDH,

I'm using a 2009 MacBook Pro, running El Capitan 10.11.5 and Firefox 50.1.0.

Click on https://www.udemy.com/30-days-of-python/

Scroll down to lecture #3 and click on the big green button with the word: "Preview" inside of it. When you click on the VDH icon, it will display the first image from above. Click any video resolution & after VDH has finished, it will display the second image above ( "No media to process" ).

Then when I play the file with QuickTime Player, the audio has some added noise & popping sounds right from the beginning. Then at the 23 second mark, the audio is skipping words and around the 36 second mark the audio is completely silent for the rest of the video. Without closing the window, if I start it around the 16 second mark I can hear the audio (albeit, choppy) until the 47 second mark, when the audio goes silent again. If I start it at the 40 second mark, I can hear the audio, until the 1:20 mark & it's silent again.

The video is choppy and twitchy around the 40 second mark, when the instructor is moving & clicking the cursor and when his display is causing the images to move.

I have purchased a VDH conversion license, but I don't know what that is supposed to do for me. I've read through the VDH & conversion manuals; & googled various sites for answers and better understanding of HLS & their issues, but I still don't know how to resolve this issue, or what I should do next. I apologize ahead of time for that.

Maybe Udemy's HLS are not in the correct format (just a guess), since I was successful in playing a Daily Motion HLS video. All of the green preview buttons, for all the courses that are in HLS format, have this issue. All the Udemy courses with mp4 format are perfect with VDH. I thank you & VDH for creating this wonderful app, that allows me to view Udemy video when I'm not connected to their web site!!!  :-)

Thank you for your time & effort to investigate & reply to this issue.

Pete

[mig]

Playing on QuickTime a video that has been captured by VDH from a HLS stream is a known issue. The choppy rendering is due to video frames not being indexed "by the book" in VDH (we do so on the fly in Javascript and the method has its limits).

There are 2 workarounds:

1. play the video with another player (VLC from http://videolan.org/ is known to work fine)
2. re-encode the video using the converter (pick the "Re-encoded MP4" format) so the stream is re-constructed properly

[Peter Rihn]

Thank you for all your assistance!

I believe my ultimate problem was that the 2 Firefox plugins (the OpenH2.64 Video Codec & the Widevine Content Decryption Module) were turned off. Once I installed Firefox 50 & turned these plugins on, all the Udemy HLS course, were switched to MP4 format and I was able to download & play them correctly as mp4 videos without any conversion. I'm guessing that the plugins affected some courses and not others.

I don't know how or if the plugins resolved my HLS issue, but maybe it will help other VDH users. Thank you MIG & VDH!

[James Davis]

VLC does NOT work. Have tried it and the voice "skips" as the video plays