FMS, MBR HDS and OSMF: Dropped frames when switching streams

hi,

 

i using fms 4.5.2 stream multi-bitrate content osmf based player.  have encoded content in mp4 containers using third party tool following recommendations given here: http://download.macromedia.com/flashmediaserver/http_encoding_recommendations.pdf

 

i have range of test content using @ 23.976, 24 or 25 fps , have created appropriate jit.conf files ensure fragments align gop size (i have tried 4s , 5s gop).

 

i targeting range of devices on both cellular , wifi connections , have range of resolutions , bitrates follows:

 

test_256x144_230kbps.mp4

test_384x216_430kbps.mp4

test_512x288_630kbps.mp4

test_512x288_830kbps.mp4

test_768x432_1130kbps.mp4

test_768x432_1530kbps.mp4

 

streaming works ok, except video freezes second when switching between bitrates. 

 

as understand it, if first frame in fragment idr keyframe (guaranteed matching fragment size multiple of gop (with fixed, closed gop)) streams should switch smoothly, different stream resolutions (for flash player >= 10.1)

 

i have tested on osmf test player (http://osmf.org/dev/2.0gm/debug.html?src= ...) range of different content (with different resolutions , bitrates, still confirming guidelines) , appears lower variants exhibit switching issue when switching bitrates same resolution.  switching between different resolutions @ higher bitrates seems work smoothly.

 

is there missing here?

 

below example jit.conf 23.976 fps source encoded 5s gop:

 

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns="http://ns.adobe.com/f4m/1.0" xmlns:hds="http://ns.adobe.com/hds-package/1.0">

    <hds:frame-rate>23.976</hds:frame-rate>

    <hds:frames-per-keyframe-interval>120</hds:frames-per-keyframe-interval>

    <hds:keyframe-intervals-per-fragment>1</hds:keyframe-intervals-per-fragment>

    <hds:hls>

        <hds:keyframe-intervals-per-media-file>2</hds:keyframe-intervals-per-media-file>

    </hds:hls>

</manifest>

 

any advice appreciated.

 

cheers,

 

chris

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