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  1. #1
    Join Date
    Aug 2013

    Default Delay in starting on-demand audio streaming

    We have an AMI for Wowza 4.0 built on m1.xlarge (64 bit, 4 core, 15 GiB RAM) EC2 instance. It is used for On-demand Audio streaming, bit rate of which varies from 32Kbps to 64Kbps. The media files are located on S3 and have following specifications:
    Format: M4a
    Codec: AAC

    The major issue in front of us right now is delay in starting the stream and there is no significant difference even if its a repeat request for the same content. The worst affected is the RTSP streaming in which the initial delay is around 8-10 seconds in a good connectivity (wi-fi /3g) and goes upto 18 seconds in case of slow networks (2G).

    The server is tuned as per the instructions in performance tuning document and I have also got all the network restrictions checked to ensure there is no UDP blocking.

    During my quest to find reason, I came across suggestions of using streaming servers which are specially designed for audio streaming applications. These servers does not add any overhead of initializing Video capabilities that are not required in case of audio streaming, which is the case with Wowza and that adds to its initial delay. Not sure how authentic this claim stands but need your opinion.

    What could be the reasons of this delay and how can I decrease it.

    Thanks in advance.

    Best Regards,
    Manoj K

  2. #2
    Join Date
    Sep 2011


    Although the AMI you're using may not be blocking UDP, it's often blocked by the mobile phone service provider.
    Do you get the same delay when using VLC player to play the RTSP stream?


  3. #3
    Join Date
    Aug 2013


    Hi Jason,

    I am using wifi and that is not blocking UDP, I got wireshark traces that shows traffic flowing over UDP, so there is no fail over that can cause delay.

    I used the same RTSP link over same wifi connection and played it using my desktop VLC and streaming starts within 4 seconds.

    My observations based on the wireshark traces for test conducted over WiFi and 3G:
    1. RTSP messages never took more than 3 seconds.
    2. There is no Fail over from UDP to TCP
    3. RTP traffic initiated immediately after RTSP PLAY message.
    4. VLC starts playing in 4 seconds.
    5. On Android stream starts in 8- 9 seconds
    6. Both Android and VLC using the same connectivity.

    So what could have been the issue that is causing delay in case of Android and how can I reduce it.

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