Odd rtmp streaming behavior: very long buffering

Forum|Forum|16 years ago
February 24, 2010
3 replies
1827 views

I've got a bunch of MP4 files: each is an H.264/AAC MP4 file. They are screencapture movies transcoded using the same tool and preset we use for lots of video (Sorenson Squish). The encodings are at 640x400, about 1.5fps, 170kbps. The videos are about 90 minutes in length.

The problem is that when streamed RTMP from FMS 3.5 (Limelight Networks), the time to buffer and play the video is very long - 60 seconds or more, easily, and no ability to navigate around in the video. Shorter videos (<5minutes) made with these exact same characteristics load and play OK. But the longer ones that have this framerate/bitrate/size won't stream right. An example is here: http://athome.harvard.edu/test/maya.html

Other, more conventional videos made with the same tools and presets also play fine. Even so, just to be sure I checked that the MOOV atoms are at the beginning of the videos. They are. The same video delivered via HTTP works fine as well.

Is there any reason that FMS would not be able to deal well with a video with this combination of size/framerate/bitrate? The encoder, codecs and formats are the same ones we use all the time, so nothing else I can think of is different...

Thanks,

Larry

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B

bengfarrell

Participant

Hey did you ever get a resolution on this? I believe that I'm experiencing the same problems. I'm seeing the buffer at 0% for the longest time, and then it'll suddenly fill up. It's also very intermittent - meaning it works most of the time, but sometimes its plain bad.

Also, it sounds like some of you guys are monitoring your RTMP traffic outside of Flash - what tools are you using for this?

thanks!

A

Anonymous

Well... if you like to see things at the byte level, there's Wireshark.

I also find Andrei's RTMP researcher to be quite helpful: http://smaxe.com/product.jsf?id=juv-rtmp-researcher

R

Robert Reinhardt

Inspiring

Can you post details about the encoding preset? The more information you can provide, the better. It could be something as simple as the frame rate 1.5 fps might just throw FMS off, but I'd have to test a few files to see--have you tried 1 or 2 fps? Also, are you using advanced B frame options in the H.264 encoding? Frame reordering on longer files could be also be throwing off FMS---I don't have any past experience with this problem, but that would be my starting point.

Also, if you want to try uploading one of these problematic files (the original source file) to my service, videoRx.com, I can see if there's an issue with the source that's causing a problem during encoding. (Starter accounts are limited to 5GB, so if you need more storage to upload the source, let me know the username you used to register on videoRx.com, and I'll set to the limit you need.) When you upload a file to videoRx.com, my system automatically creates a thumbnail of the video using the same frame rate as the source. I use FMS to stream previews of uploaded content, so I'm curious to know if your content creates the same problem on my servers.

-Robert

A

Anonymous

Hi Robert,

Thanks for looking at this. The preset is a Squeeze preset,being executed by Squish (Sorenson's web-based client-side encoding product). I did try re-encoding with the keyframe interval at every-two-frames, which comes out to every second or so. That did not make any difference. I've uploaded the file to videoRx....username lbouthillier.

<!DOCTYPE squeeze_audience>
<Output DefaultName="MP4-squish-006.xss" Id="172875120" IsLite="False" IsMBR="False" Name="Large Size, Standard Quality (900kbps 640x480)" OutputFormat="MP4OutputFormat" SubOutputFormat="Adobe Flash 9+ (F4V)" UsingCustomFilter="False" Version="5.0" Workflow="Sorenson 360\squish">
    <PlayerOptions Name="" OutputFormat="MP4OutputFormat">
        <AddHintTrack Value="False"/>
        <VideoLocation Value="LinkedFlv"/>
        <LinkedFlvPath Value=""/>
    </PlayerOptions>
    <AudioCompressor codec="Coding Technologies aac">
        <DataRate Value="96000"/>
        <SampleRate Value="44100"/>
        <SampleSize Value="16"/>
        <ChannelMode Value="ChannelModeStereo"/>
        <SubOutputFormat Value="None"/>
        <PacketSizeEnable Value="False"/>
        <PacketSize Value="1450"/>
        <MediaKeyEnable Value="False"/>
        <MediaKey Value=""/>
    </AudioCompressor>
    <VideoCompressor codec="MCptH264">
        <DataRate Value="804000"/>
        <FrameRate Value="-1"/>
        <OutputSize Height="480" Width="640"/>
        <MaintainSourceAspectRatioEnable Value="True"/>
        <LetterBoxOrPillarEnable Value="False"/>
        <BitRateMode Value="BitRateModeOnePassVBR"/>
        <KeyFrameRateEnable Value="True"/>
        <KeyFrameRate Value="300"/>
        <AutoKeyFrameEnable Value="True"/>
        <AutoKeyFrameSensitivity Value="50"/>
        <MaxDataRatePercentEnable Value="True"/>
        <MaxDataRatePercent Value="150"/>
        <ExtendedPluginSettings>
            <Profile Value="Baseline"/>
            <InterlaceMode Value="Progressive"/>
            <FieldOrder Value="Top Field First"/>
            <Quality Value="Best"/>
            <NumberOfBFrames Value="0"/>
            <CABAC Value="No"/>
            <NumberOfSlices Value="Auto"/>
        </ExtendedPluginSettings>
    </VideoCompressor>
</Output>

A

Anonymous

Had a look... seems like there's delay in limelight serving the video. When I seek, I see no data moving across my network interface for the first 10 seconds or so. Once data starts coming in, playback is fine.

At first guess, I'd say this is a Limelight issue, rather than an FMS issue. Has limelight support been able to offer any advice/answers?

A

Anonymous

I have engaged limelight on the issue. They've determined that it's not a network issue, but are looking at the possibility of an issue beween the file itself and FMS. No real news, yet, though.

A

Anonymous

So it looks like this is an FMS issue. The page at http://athome.harvard.edu/test/maya.html demonstrates a file streaming from FMS on Limelight and Cloudfront. In both cases, initial load time is very very lengthy, and seek time is poor as well.

The mp4 is about 170kbps, about 1.5 fps, with keyframes usually over a minute apart, sometimes several minutes. I'd thought that it might be a keyframe interval issue, so I re-encoded with a keyframe every 2 seconds (see the third video on the page). No change tot he load/seek behavior.

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