Warnings when using media stream validator on HLS VOD content

Wowza Streaming Engine
1

Hello, we are trying to build an iOS App which uses HLS VOD content however when we attempt to validate the streams using the Apple media stream validator we get the following errors.

media_3.ts?wowzasessionid=1344685693:
        WARNING: Media segment bandwidth exceeded target playlist bandwidth by 11 % (419.46 kbits/sec vs.378.04 kbits/sec, limit is 10 %).
media_9.ts?wowzasessionid=1344685693:
        WARNING: Media segment bandwidth exceeded target playlist bandwidth by 12 % (424.80 kbits/sec vs.378.04 kbits/sec, limit is 10 %).
media_16.ts?wowzasessionid=1344685693:
        WARNING: Media segment bandwidth exceeded target playlist bandwidth by 11 % (421.12 kbits/sec vs.378.04 kbits/sec, limit is 10 %).

I have just included a small subset here, for the example file above we had 24 of these warnings for a file segmented into 129 ts chunks. This was with version 3.0.5, I have also tried it with version 3.5 which is better, but it still had 7 warnings for the same file.

I’m slightly confused as to what could cause these warnings, and is there a way to stop them from occurring? I know Apple in theory shouldn’t reject an App with warning messages but we have found that hasn’t always been the case.

Many thanks

2

Hi

Is your content in multiple bitrates and are you accessing them though a .smil file?

If you are, you may have to raise the bitrate you’re declaring in the .smil file as it is out by more than the 10% limit stated in the logs you provided above.

Jason

3

You can wrap the single stream in .smil file and follow that guide to add adjusted system-bitrate. Change it to whatever the validator likes.

btw, you might need a 64kbs audio rendition for app store compliance.

https://www.wowza.com/docs/how-to-create-apple-app-store-compliant-streams

Richard

4

Yes, I think that is right. Also check against this formula:

kilobytes on disk * 8 / duration in seconds = kbs

Richard

5

Hi

Wowza does try and average the bitrate however if the bitrate varies too much then you will experience this kind of problem and Wowza can’t do anything about that by itself.

Try adding the configuration shown here,

https://www.wowza.com/docs/how-to-add-resolution-and-codec-metadata-to-ios-streams

Jason

6

Hi,

No, this is a single bit rate stream, the bit rate stated in the m3u8 is what Wowza returns

thanks

7

Thanks,

I’ve had a look at the link but it states that it is already enabled by default on Wowza 3 unless I’m looking at the wrong section?

Just so I understand the issue completely, Wowza will take an average bitrate value of the whole file and use that to fill in the metadata section of the m3u8 file. However if the natural fluctuations in the bitrate (even with CBR) mean that it is more than 10%, this error will be generated.

Simon

8

Many thanks, that all makes sense.

One final question. When Wowza calculates the average bitrate of a file does it take into account the size of the headers and add it on accordingly? I have a file which all desktop applications (VLC, GSpot, FFMPEG) reports as 343kbps whereas the m3u8 which Wowza generates reports it as 378.04kbps. I’m trying to work out why there is a discrepancy.

Simon