Mobile Streaming vs Desktop Streaming

November 27, 2013

I recently complete an edit for a client in which he recorded a few video segments for his health and nutrition business. Everything appeared fine on local playback so I uploaded it to Youtube for him to approve. Imagine my surprise when he emailed me to let me know there was something wrong with the audio. I listened to my local copy again and admitted there was a quite a bit of wind noise when it was originally recorded so I tweaked the audio and uploaded it again. And again I received the same complaint: bad audio.

I went online and took a listen to the Youtube version from my workstation and didn’t hear any *real* problem but I did notice that when I tweaked out the wind noise earlier I had reduced the highs a little too much. I admitted that I should have caught that when I originally listen to it but I was beginning to wonder how picky this client of mine was that he could pick up on the slight tinniness of his voice. So I tweak it, again,  in Sony Vegas and uploaded it again.

And I received the same complaint from the client: there was still a problem with the audio!

Now I was baffled and a bit… upset. Just how picky was this guys ears. I checked the YouTube copy from another computer and another computer and couldn’t find anything that should cause me to redo the edit. And then he provided one crucial detail for me: he couldn’t hear it properly from his phone.

His phone?

So I brought up the link on my cellphone to get a good listen to it and it did indeed sound like garbage. The video was the same but you couldn’t hear the speaker while the background music sounded fine. How was it that viewing the link from my desktop provided a good quality version but watching the same link from my phone produced such a horrible result? So off to Google I went to search for this strange phenomenon.  I had to phrase the question a few different ways to get the answer I wanted but finally came across the following thread on Creative Cow forum website. Someone was having trouble with their audio after uploading to Youtube and the problem only affect mobile devices. Hmmm, that sounded familiar. The key to the answer came when a response on the forum pointed out the following thing:

“Muffled? Sounds like a out of phase type issue, which would leave alone music and sound effects for the most part.” (thanks Bret Williams)

At that point I remembered something important. When I first started editing this set of audio files I had noticed that though my master audio levels were even the files showed my right channel much louder than my left. I hadn’t panned the audio channel and I didn’t want one side to be louder than the other so I unlinked and then adjusted the master level by pushing up the left channel to even out the audio levels. It seemed in doing that I had placed the audio out of phase. Audio Edit I tried to render the audio out to a Sound Forge and render the file back to a mono track and import it back into Vegas but still had the same issue from mobile devices. I tried a couple of other things that didn’t solve the problem and finally I decided to put the master channels back to their original settings, render the file and see how that worked. Voila, Success. Audio on mobile devices sounded just like the desktop. It appears that Youtube compressed the audio from a stereo signal to mono and in doing so put the vocals out of phase.

I knew that Youtube recompresses the videos that I upload even though I try to get as close as possible to what they suggest but I didn’t know about the separate mobile stream. (I guess I never gave a second thought to the option that allowed mobile playback or not.) Why the need for a separate stream for mobile devices? Well, when you consider that not all US mobile users are on unlimited data plans not having to download a stereo audio signal makes some sense. Not all cellphones would even benefit from trying to play audio in stereo though more and more are using a combination of hardware and software imaging to create a stereo sound.

As an additional test I uploaded the original video that turned out bad on Youtube to my Vimeo channel and had no issues with bad audio on playback so it appears that this is definitely something that Youtube does when you upload a video. This means another step in my workflow when uploading video to YT; it is no longer enough to test the uploads with my desktop. Now I need to test all uploads with my phone as well.

BTW – I haven’t been able to discover why those sets of recordings had different audio levels between my left and right channel as none of the other recordings I did that day suffer from that problem. More testing to come.

Here is the final video on Vimeo


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