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Thread: Quality Dropping Periodically

  1. #1
    Join Date
    Apr 2013
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    Exclamation Quality Dropping Periodically

    I'm using the transcoder addon for Wowza 4.0.3 to take a 720p 1.6 Mbps stream and drop it down to a 360p 0.4 Mbps stream for IOS/Android. The lower quality stream generally looks good, but occasionally, every few minutes or so, the quality drops and the image gets very blurry and pixelated. After looking at the performance monitor, I can see the CPU spike at same time as the image getting blurry. The server CPU hovers around 20-30% and when it spikes, it only hits 40% or so. The server is a Virtual machine running on VMware with two dual core CPUs assigned and 6 GB of RAM. I've checked the Java Tuning guide for Wowza 4 and it basically says to set everything to automatic, which it is. I do have it running in production not developer mode. I know it's not a network issue, because my old encoder does transcoding and it can send out both stream and they run through the server to the same endpoints with no trouble. Is there anything I can do to prevent these drops in quality?

  2. #2
    Join Date
    Dec 2007
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    Do you see any messages like this in the access log?

    TranscodingSession.updateBehindFilter[transcoder/_definst_/myStream]: Video behind filter state change. New state: SKIP1FRAME
    TranscodingSession.updateBehindFilter[transcoder/_definst_/myStream]: Video behind filter state change. New state: ALLFRAMESON
    If so, this means that machine is not keeping up with transcoding. Take a look at the Transcoder Benchmarks to get an idea of server capabilities and limitations.

    Richard

  3. #3
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    Apr 2013
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    I didn't find those specific errors, but I did find these.

    WARN server comment 2014-04-09 03:18:54 - 26.664- LiveStreamPacketizerSmoothStreaming.handlePacket[live/_definst_/offline_low]: Fragment duration greater than suggested range of 1-4 seconds. Adjust keyframe interval accordingly: Fragment durations: [4.9,4.9,4.9]
    WARN server comment 2014-04-09 18:40:53 - 55346.337 - SanJosePacketHandler.handlePacket[live/_definst_/high]: Timecode out of order [video]: 55358366:55358833
    WARN server comment 2014-04-09 18:40:53- 55346.338- LiveStreamPacketizerSmoothStreaming.handlePacket[live/_definst_/high]: Timecode out of order [video]: 553583660000:553588330000
    WARN server comment 2014-04-09 18:40:53- 55346.338- CupertinoPacketHandler.handlePacket[live/_definst_/high]: Timecode out of order [video]: 55358366:55358833
    WARN server comment 2014-04-09 18:40:54- 55346.94 - LiveStreamPacketizerPacketHandler.handlePacket[live/_definst_/high]: Timecode out of order [video]: 55358366:55358833
    I used to run key framing every 120 frames which is the Wirecast default I believe. I changed it to 60 the other day, and I think it reverted to the old setting. I've updated that and will see if it helps. Any thoughts on the time code errors? They would have been around the time we were broadcasting last night.

  4. #4
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    This is Wowza reporting on what it is receiving, which is an issue either with the network or the encoder. It might be inadequate connection on the encoder side.

    Richard

  5. #5
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    Apr 2013
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    We ran a broadcast again last night. There were no errors in the log and it was still exhibiting quality issues on the transcoded stream. I don't think it's a bandwidth issue, we ran transcoding locally on the encoder for a full year before we switched to server side encoding and we didn't have any bandwidth issues before. The server and encoder are on the same LAN connected at 1 Gbps. Our VM server is reasonably close to Server 1 on the Transcoding benchmark. We are just running a single transcode, 1.6 Mbps to 0.4 Mbps, and the CPU is only peaking at 40%. Is there anything else that I can check or update to help this?

    PC Normal


    PC Quality Drops


    Android RTSP Quality Drops


    Server Performance

  6. #6
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    Do you see the same in RTMP playback in the desktop? Android is difficult. What are the frame sizes? Try these frame sizes:

    800x480
    480x320
    240x160

    Also make the video Profile Baseline, if not already.

    Richard

  7. #7
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    Apr 2013
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    Here are my encoding settings. I'm not running at any of those suggested resolutions, but the problem shows up on both Android and Flash player (JW player). I used to run these exact setting encoding both on Wirecast rather than using Wowza to transcode and I did not have issues with Android or Flash. The reason I am not using Wirecast for transcoding now is because sometimes we use a Teradek Vidiu for events which can only send one stream and I don't want to have to reconfigure the server every time we have an event outside our main recording area.

    Source from Wirecast

    Codec: H.264
    Resolution: 1280x720
    Frame Rate: 30 fps
    Av Bit Rate: 1500 kbps
    Profile: High
    Key frame every: 60 frames
    Audio: 128 kbps

    Transcode Settings
    Codec: H.264
    Resolution: 640x360
    Frame Rate: 30 fps
    Av Bit Rate: 450 kbps
    Profile: Baseline
    Key frame every: 60 frames
    Audio: 128 kbps (passthrough)

    From everything I read these settings should work fine and shouldn't be taxing the server. The CPU shows that the server is not being taxed, but the quality is still poor. Is there anything else I can try?

  8. #8
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    Ethan,

    I think we'll have to take a closer look. First re-start Wowza, start up the stream and test playback in Flash on the desktop and Android device, then zip up the /conf and /transcoder folder and the current access log showing your re-start and tests and send to support@wowza.com. Include links to your stream, and include link to this post for reference

    Thanks,
    Richard

  9. #9
    Join Date
    Jul 2011
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    104

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    Hey guys!!

    Been a while since I posted, so hope all is well with the Wowza team.

    Seeing some weird stuff with using the transcoder regarding quality at lower bitrates, similar to what the OP was experiencing, except we don't have any CPU spikes or lines in the logs that suggest an issue with either the source stream, hardware, or transcoder itself.

    Some background info:

    We're sending a very small stream (640 x 360) at 3 different bitrates: 1200, 500, 200. Once the audio is added they become 1392, 692, and 392. The profiles for the 692 and 392 bitrates are passthrough for framesize, keyframe interval, audio codec, etc. We're only adjusting the bitrate itself down from the input source at 1392 (1200 + 192).

    At some points, usually when there is a lot of movement on the source stream, the quality of the lower bitrates gets really, really poor. Very blocky, but no stuttering or jerky movements. Only very pixelation and visual distortion, the audio however, is fine, no issues.

    Video is h264 w/ AAC audio, 640 x 360 - Main profile 4.1. Serving to desktop clients, not mobile devices.

    Any insight? Lemme know if you would like / need more info, I'd be happy to provide it! )

  10. #10
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    Jul 2011
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    bump?

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