4 Replies Latest reply: Jun 25, 2010 5:46 PM by BrandonC RSS

    A/V syncing issues

    Morac Newbie

      I've been disappointed with the iPhone app pretty much since I first purchased it.  The quality isn't that good (even over WiFi), the video seems to run at about 15 fps rather than 30 fps (even over WiFi) and more annoyingly is that the audio almost always seems delayed a bit (yes, even over WiFi).  This is with a Sling Pro HD.

       

      I originally contacted support, but was underwelmed by their response and didn't follow up.  Of course now I'm out of warranty on the iPhone app (not that they would have refunded the purchase anyway).

       

      I've discovered the app only uses around 512 kbps over WiFi.  That's probably a limitation of doing software decoding of video rather than hardware decoding.  Of course if the Sling sent out H.264 video instead of WMV this wouldn't be an issue.  The Sling Pro HD supports H.264, but it's not used.  Why is that?

       

      Second the frame rate is around 15 fps, despite being advertised as 30 fps.  I'm guessing it's because of the low bitrate, though I've watched YouTube videos on my iPhone with not only better framerate, but better quality.  Again those are H.264 video.

       

      Oh and the audio/video is usually out of sync for HD video and sometimes for SD.

       

       

      Are there any plans to update the iPhone app to fix the quality and syncing issues?

        • Re: A/V syncing issues
          eferz Expert

          Morac wrote:

           

          I've been disappointed with the iPhone app pretty much since I first purchased it.  The quality isn't that good (even over WiFi), the video seems to run at about 15 fps rather than 30 fps (even over WiFi) and more annoyingly is that the audio almost always seems delayed a bit (yes, even over WiFi).  This is with a Sling Pro HD.

           

          I originally contacted support, but was underwelmed by their response and didn't follow up.  Of course now I'm out of warranty on the iPhone app (not that they would have refunded the purchase anyway).

           

          I've discovered the app only uses around 512 kbps over WiFi.  That's probably a limitation of doing software decoding of video rather than hardware decoding.  Of course if the Sling sent out H.264 video instead of WMV this wouldn't be an issue.  The Sling Pro HD supports H.264, but it's not used.  Why is that?

           

          Second the frame rate is around 15 fps, despite being advertised as 30 fps.  I'm guessing it's because of the low bitrate, though I've watched YouTube videos on my iPhone with not only better framerate, but better quality.  Again those are H.264 video.

           

          Oh and the audio/video is usually out of sync for HD video and sometimes for SD.

           

           

          Are there any plans to update the iPhone app to fix the quality and syncing issues?

           

          Actually, the Slingbox Solo and  the Slingbox Pro-HD will stream H.264 and AAC to the iPhone and the Web Slingplayer for Mac.  I'm not sure where you're getting your information but could it be a misquote from Dave Zatz interview with Dave Eyler?   I've noticed a lot of sites misquoting the original article.

           

          http://www.zatznotfunny.com/2010-03/whats-next-for-slingplayer-mobile-ipad/

           

          I recently checked in with my former Sling peeps, regarding mobile clients. Specifically, codecs and resolution. As we know, a Slingbox Android client is on tap this summer. And I wondered if they’re sticking with WMV video streaming or moving to H.264 for this platform. While I wasn’t able to get a definitive answer on Android from Mobile Product Marketing Manager, Dave Eyler, I have learned  they’re  “actively moving towards H.264″ – which requires the newer, more capable placeshifters (think SOLO or PRO-HD).   Also, it’s really no surprise that they’ll be going the Silverlight   route for Windows Phone 7.

           

          In regards to resolution, I don’t don’t believe  Sling Media has taken mobile client video resolutions beyond 320×240.  By design, due to  processing power, memory, bandwidth and battery life.  But, here comes the iPad. And I don’t want a pixel-doubled iPhone SlingPlayer  app on that large screen. Fortunately, Sling has confirmed they’re prepared to accommodate me with something a bit better, some  day…

           

          I've been using the Slingplayer for the iPhone since it  was released and have never seen an audio video synchronization issue.   And I've used it on both the iPhone 3G and 3GS.  If there are quality issues, its more likely due to the down resolution  and encryption that's being applied to the stream.

           

          Remember, the Slingbox employs SlingStream 2.0 technology which is a fancy way of saying it uses an encrypted variable bitrate stream that encapsulates H.264 or WMV video and AAC, WMA, or PCM audio.  And the Slingplayer will dynamically adjust and compress the stream based on the network and hardware performance of the client.  It is not a fixed rate stream as you assume.

           

          Also, you shouldn't compare a prerendered stream from youTube with an live transcoding stream from the Slingbox.  Even with equal encoding configurations, the quality from a pre-encoded stream will always outperform live transcoding.

            • Re: A/V syncing issues
              Morac Newbie

              I don't see how the iPhone app could be using H.264 since the app works will all the old Sling boxes and they don't support H.264.  “Actively moving towards H.264″ isn't the same thing as currently supporting H.264.  Unless there's an update to the iPhone client that only works with the SOLO and PRO HD, it can't be using H.264.

               

              As for the A/V sync problem, do you try to use Sling Player on HD channels?  That's where I mainly see it as did many people on the old Sling Community sight.  SD channels are relatively okay.

               

              Also Slingbox may adjust the stream bitrate for desktop players, but for mobile players, it's locked to a maximum of 500 kbps for Wi-Fi and 120 kbps for 3G/Edge.

               

              There was a lot of research on the iPhone player back in the the old SlingCommunity forums so it's pretty much known what its limitations are.  Here's an example about the limits thanks to Google's cache.  BTW those numbers haven't changed since the post.  You can check your own size.plist file in the SlingPlayer.ipa, which is just a zipped file.

               

              The Slingbox should be able to do better realtime muxing of audio/video at 320x240 (or 256x192) resolution, especially with a 20 second buffer.

               

              Basically it comes down to that, Slingbox Pro HD itself is capable of outputting HD video over a network and even downconverting it to QVGA.  QVGA still looks good on a PC and the A/V is in sync for the most part (a lot of skipping on a DVR can desync it), but not on an iPhone.

                • Re: A/V syncing issues
                  eferz Expert

                  Hey thanks for that, I completely forgot I could do that.

                   

                  From Google Cache...

                   

                   

                  3GBitrate.png

                   

                  <dict>
                          <key>AnimationDurationForCurl</key>
                          <string>0.75</string>
                          <key>AnimationDurationForFadeIn</key>
                          <string>0.5</string>
                          <key>AnimationDurationForSlideIn</key>
                          <string>0.3</string>
                          <key>AnimationDurationForSlideInForStreaming</key>
                          <string>0.5</string>
                          <key>AnimationDurationForVerticalFlip</key>
                          <string>0.75</string>
                          <key>ChannelLogoViewTimerDelay</key>
                          <string>2.0</string>
                          <key>ChannelUpDownViewTimerDelay</key>
                          <string>2.0</string>
                          <key>ConnectionDescription</key>
                          <string>iPhone SPM</string>
                          <key>EnvironMent</key>
                          <string>PROD</string>
                          <key>HighQualityVideoHeight</key>
                          <string>240</string>
                          <key>HighQualityVideoWidth</key>
                          <string>320</string>
                          <key>LowQualityVideoHeight</key>
                          <string>192</string>
                          <key>LowQualityVideoWidth</key>
                          <string>256</string>
                          <key>Max3G_EDGE_TotalBitrate</key>
                          <string>250</string>

                          <key>MaxFrameRateFor3GS</key>
                          <string>15</string>
                          <key>MaxFrameRateForOthers</key>
                          <string>15</string>
                          <key>MaxMajorDigitCountForChannelEntry</key>
                          <string>5</string>
                          <key>MaxMinorDigitCountForChannelEntry</key>
                          <string>5</string>
                          <key>MaxWifiTotalBitRate</key>
                          <string>500</string>
                          <key>MinimumMemoryToShowLowMemInMB</key>
                          <string>5</string>
                          <key>PlayerCountry</key>
                          <string>US</string>
                          <key>RemoteFileName</key>
                          <string>SBAV.cfg</string>
                          <key>SlingGuideVersion</key>
                          <string>1.0.7.2</string>
                          <key>SwipeErrorViewTimerDelay</key>
                          <string>3.0</string>
                          <key>URLs</key>

                   

                  So, it appears that the file has changed.

                    • Re: A/V syncing issues
                      BrandonC Novice

                      eferz wrote:

                      So, it appears that the file has changed.

                       

                      I think that changed on the last version the put out of the player.

                      Wonder if anyone has tried treaking the plist on their iPad for a better experience and if it helped. Could be interesting.