Improving Quality of Meeting Recordings


By Tolga Kilicli, Product Owner, Microsoft

We released the Lync 2013 client for Windows almost a year ago, which included some changes to how calls and meetings are recorded. Those changes included introducing MP4 as the recording format to make recordings more broadly accessible across different devices and applications. As a side benefit, MP4 recordings are processed much faster on Windows 8 thanks to support for hardware acceleration.

We also discovered and received feedback on some problems with the recording feature in Lync 2013, principally:

  • Meeting recording files got larger – too large to be uploaded or easily shared, which is important to people who use Lync recordings for training or knowledge sharing.
  • Meeting recording quality got worse, much worse in some cases.
  • These issues are interrelated – higher quality recordings usually result in larger files, all else being equal. We made some changes in a subsequent update to Lync 2013 for Windows (the CU2 update), which fixed the size but made quality even worse.

So we took a harder look at the different parameters for meeting recordings – what we could change, and why. We looked more closely at the nature of what is being recorded, in terms of screen refresh and motion and text and graphics resolution.

Analysis and user testing

Based on our analysis and useful customer feedback, we calculated a new set of recording resolutions, frame rates, and bitrate ranges. We aimed to increase the resolution of recordings yet also provide smart tradeoffs with recording size, so we landed on 3 different resolutions options: 480p (854×480 pixels), 720p (1280×720) and 1080p (1920×1080). We also increased the frame rate from 10 to 15 frames per second – not quite movie quality, but sufficient to capture PowerPoint animations and document scrolling. That improved frame rate plus the resolution options were designed to produce sufficiently high-quality recordings and yet allow users to pick their preferred balance between recording resolution and file size.

But how would that work in the real world? Before shipping an update to Lync client recording, we tested these options and few others by taking a set of real meetings and creating recording using a range of settings. We also varied the maximum bitrate of the recording, which impacts both quality and file size. Then we came up with perceptual measures of video quality, such as readability of text, animation smoothness, and image clarity.

We talked to a small group of users, had them watch different versions of the same recorded meeting (with different options), and asked them to rate each video for each perceptual measure. The results are shown below:

 

These results led us to a few conclusions:

  1. The 15 fps frame rate is necessary for sufficient quality, regardless of resolution.
  2. Lower bitrate (kbps) for lower resolutions does not cause a significant decrease in quality.
  3. Increasing bitrate without changing resolution improves quality up to a point but beyond that point quality does not significantly change.

We then finalized the options that are now available in the latest update of the Lync 2013 client for Windows:

 Resolution   Bitrate, Frame Rate  Estimated file size for 1-hour meeting (observed on Windows 8*)
 480p (854 x 480)   500kbps, 15fps   150MB
 720p (1280 x 720)   1250kbps, 15fps   250MB
 1080p (1920 x 1080)   2500kbps, 15fps   400MB

 

 

 

 

Which option to choose?

We worked on the 720p resolution to provide a good quality in a size that would fit in SharePoint 2013's default max file size limit for uploading to lists. Even though file size is dependent on the content in the video, in our tests for regular meetings we have seen 1-hour, 720p recordings to be less than 250MB on Windows 8 PCs. Also if you are using SkyDrive Pro, you can share your videos by just putting them in the local synchronized folder and sharing them with your colleagues. SkyDrive Pro also offers 25GB storage and 2GB upload limit with SharePoint Online

For a meeting that did not have much content shared, or if file size is more important for you compared to readability of text or fine details on the content shared, you might want to consider the 480p resolution.

On the other hand, if you intend to view or present the recording on a large screen (wall display, TV), and you have multiple things being shared in addition to videos of participants (e.g. screen sharing), then the 1080p option will work much better. And the 720p option sits in the middle as the default choice and gives decent quality, decent file size, and decent resolution for most users.

To change the option used for your recordings, go to the Lync Options dialog (Tools > Options) and find the Recording tab:

 

Recording Manager follows these settings and when you "Publish" a meeting to an MP4 file the output will be in your selected resolution:

 

This also gives you an option to change the resolution in the options dialog and "Publish" your meeting again in the resolution.

We look forward to hearing your feedback on these updates and improvements to the recording feature.

*Codecs shipped in Windows 8 provides more granular control over encoder parameters. File size might be different and higher on Windows 7 as a result.


Comments (30)

  1. Anonymous says:

    We were using Lync to record video interviews that we can “ship” to our representatives, but found out afterwards that majority (>80% of the video feed) was not captured. Any idea on what caused the problem and how I can avoid it? we are scheduling a retake for these interviews and would hate for it to happen again.

    XY Mesina
    Philippines
    xymesina@gmail.com
    +639266602542

  2. hassan sayed issa20014 says:

    Thanks

  3. Anonymous says:

    Oh, I also have the Skype for Business Tech Preview, so I might see what I can do with that.

  4. Anonymous says:

    Thanks for the great article Tolga, particularly the explinations behind the decisions.

    However it would appear that a number of us (vocal minority?) are still experiencing video quality issues with the Lync 2013 recordings.

    In particular, I’ve been experimenting with corporate branded PowerPoints and I’m finding three main issues:
    1. Colour matching is way off.
    2. Significant colour banding.
    3. Obvious ghosting of text and hard edges (colour bleed?)

    It’s like watching very early DivX encoded movies with very low bit rates.

    I’ve tried both 720p and 1080p and both end up with bit rates that rarely hit a quarter of the rates you state above. This is somewhat understandable, since the PowerPoint is fairly simple with no complex animations or page transitions, but I would expect H264
    to do a much better job, but it’s like your implimentation is trying trying way to hard to reduce bitrates.

    At the end of the day, the quality of the resulting video isn’t really something I want to be showing to Clients.

    What are our options going forwards?

    FYI Happened to test on Lync 2013 client v 15.0.4615.1000 – May 2014 update.
    I also have available 15.0.4693.1000 – which I think is the Feb or March 2015 update.

    Thanks
    Craig

  5. Peter says:

    Would there be any benefit from converting the .MP4 to a FLV format?  I am not sure if this would actually reduce the file size significantly enough to justify a loss in fidelity, but it would be great to reduce the file size.  Even better would be to stream them.

    Great article either way.

  6. user says:

    Great technical detail – thank you for this.

    One feature that is missed from the 2010 version of Lync Recording Manager is the ability to set a start and end point when publishing a recording.  It was extremely useful for users like me who record a high number of meetings and often have requests to segment recordings after the fact, and also lets us create more professional-looking recordings by trimming any extra footage at the start and end of a recording.

    I found an article on using Windows Movie Maker to edit Lync 2013 recordings, but I tried it out and it impacts quality too much.  (blogs.technet.com/…/working-with-lync-2013-meeting-recordings.aspx)

    Since there is still an ability to re-publish a recording at a different resolution, and re-publish with different content parameters, it would seem that the Recording Manager is still working from 'raw' files in some sense.  Assuming that is the case, it should be possible to include this functionality.

    Any chance we could see it restored in the next version?

  7. Kay Morten Myrbekk - kay.m.myrbekk@hint.no says:

    Thank you for a detailed article.

    With the recording features introduces the latest year with increased sound quality and now better video quality things is getting very good. For record of lectures and meetings with video and screen sharing things are now good enough.

    Still there is a problem with video quality when not sharing any content. At our point, i looks like the quality has decreased since Lync 2010. This is a problem while we at our University we are also using Lync to record for instance:  

    – Record how students perform in the nursing lab.

    – Instruction videos on how to measure blood procure.

    – Screencast for teacher while filming whiteboard or his notebook.

    – ++

    We very much would like the video to be at least 24 frames pr. second and the video should match the 720p and 1080p option. It is a bit misleading with the quality option while the video is still 15 frames pr. second and a bit blury in full screen. We would
    very much like another option were also the video recording is 720p HD while creating these videos.

    Another challenge is when the teacher record lectures. When the recording is started and even more when the recording is paused it should be more visible. The teachers often forget to start an paused recording while there is no "blinking pause lamp" or other
    visible signs expect an small icon. The pause sign should in some way be more visible like in Camtasia relay. There is an big difference recording an meeting in front of your own computer at the desk and preforming in front of an crouwd. Things should be as
    easy and visible as possible for recording lectures, seminars and other happenings when the speaker is also the "director".

    Thank you for a great job in the last year with the recording feature in Lync 2013.  We have now stopped using other screen recording software and use Lync big time to record lectures and meeting. We also use it in auditoriums where it is removes less flexible
    and more expensive AV systems. With the small adjustments I describe here, it would be close to perfect also in these scenarios.

    Regards

    Kay Morten Myrbekk

    Mobile: +47 922 08 613

    email: kay.m.myrbekk@hint.no

    Our UC blog (translated)
    translate.google.no/translate

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  23. Daniel says:

    We’re having a weird problem with how Lync 2013 creates the MP4 file/headers.

    Usually, when you create an MP4-file for publishing on the net, you place all the header data at the beginning of the file. This is required for fast start streaming since it tells the media player how long the file is without having to download the full file before it can start playing. Adobe Media Encoder does this, Techsmith Camtasia too.

    However it looks like Lync 2013 stores that information last in the file? The behaviour we see is that the whole file has to be downloaded locally before the file starts playing and together with Win 7 / WMP 12 / SP 2007 / Swedish characters we can’t play them at all unless you open the SP-folder in WebDAV (explorer) mode.

    The solution was to use the little open source utility qt-faststart ( http://ffmpeg.zeranoe.com/builds/qt-faststart/ ) to rewrite the header and put all the information at the beginning of the file. It only takes a few seconds and the resulting MP4-files work as they should and start playing directly without the need to first download a say, 300MB recording.

    I simply don’t understand why Lync 2013 can’t do this in the first place, considering how much better the header fixed files work with your own web browsers and Windows Media Player. Sure, it’s a quick fix to rewrite the headers but we have over 8000 users here and can’t expect them to use a command line utility before publishing their recorded meetings to Sharepoint.

    Please consider changing this for a future update.

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  25. Arnt says:

    Why not give us the option to control the framerate? 15 is useless when video is an issue.

  26. Nick says:

    At least Lync 2010 had a raw files directory where we could pull individual video, audio and screen content into an editor and edit and fine tune the compression to suit our needs. We would LOVE this to be available once more – especially if the raw video files were higher frame rate. Until that’s available, the Lync 2013 recording feature is a step backwards from Lync 2010. We’re using other screen capture tools for now. We get more flexibility and higher quality.

  27. John says:

    My Linc 2013 does NOT have the "Recording" option. It has all the others listed. What do I do about this?

  28. Scott S. says:

    In Lync 2010 the meeting were much smaller, our meetings are really just Audio and a PPT. But we need to put the recordings up on SharePoint so our other offices can watch it.. Problem is they are all have low bandwidth.
    Is there anyway to just record the audio, then I can post the PPT.
    thx

  29. Ajie says:

    HiTolga ,
    Thanks for this nice article. We figured out that standup meetings are great but needed improvement (they took a lot of time, de-focussed our colleagues and interrupted their workflows). Because of this we developed a SaaS tool to "automate" the daily standup
    meetings – with just a single email. If you like to take a look: http://www.30secondsmail.com.

    Best,
    Ajie

  30. Ajie says:

    HiTolga ,
    Thanks for this nice article. We figured out that standup meetings are great but needed improvement (they took a lot of time, de-focussed our colleagues and interrupted their workflows). Because of this we developed a SaaS tool to "automate" the daily standup
    meetings – with just a single email. If you like to take a look: http://www.30secondsmail.com.

    Best,
    Ajie