Dash-Outputs with QVBR always exhaust the maximum bit rate allowed

Question

Hi, we are creating HLS- and DASH-Outputs via MediaConvert (1080p, 720p, 480p, 360p).

While testing our transcoded playlists on [Bitmovin's test environment](https://bitmovin.com/demos/stream-test?format=dash&manifest=https%3A%2F%2Fbitmovin-a.akamaihd.net%2Fcontent%2FMI201109210084_1%2Fmpds%2Ff08e80da-bf1d-4e3d-8899-f0f6155f6efa.mpd), we noticed that our DASH content is always loaded with the bitrate which we set as the maximum value for QVBR (Single Pass HQ, no fine tuning). In contrary our HLS content is loaded with a variable bitrate which was considered suitable by MediaConverts rate control mode QVBR (so I think).

Since our encoding settings for DASH and HLS  are identical, we wonder if that behaviour is "correct".
If someone could take a look at this issue, it would be much appreciated.

In the following you'll find a  [Hls-Playlist](https://ardplus-public.s3.eu-north-1.amazonaws.com/output/test/encoding-test/default/1080p_8000_qvbr9_720p_6000_qvbr8_480p1000_qvbr7_360p_1000_qvbr7/mord_mit_aussicht/hls/hls.m3u8) ([Bitmovin-Hls-Link](https://bitmovin.com/demos/stream-test?format=hls&manifest=https%3A%2F%2Fardplus-public.s3.eu-north-1.amazonaws.com%2Foutput%2Ftest%2Fencoding-test%2Fdefault%2F1080p_8000_qvbr9_720p_6000_qvbr8_480p1000_qvbr7_360p_1000_qvbr7%2Fmord_mit_aussicht%2Fhls%2Fhls.m3u8)) and [Dash-Playlist](https://ardplus-public.s3.eu-north-1.amazonaws.com/output/test/encoding-test/default/1080p_8000_qvbr9_720p_6000_qvbr8_480p_1000_qvbr7_360p_1000_qvbr7/mord_mit_aussicht/dash/dash.mpd) ([Bitmovin-Dash-Link](https://bitmovin.com/demos/stream-test?format=dash&manifest=https%3A%2F%2Fardplus-public.s3.eu-north-1.amazonaws.com%2Foutput%2Ftest%2Fencoding-test%2Fdefault%2F1080p_8000_qvbr9_720p_6000_qvbr8_480p_1000_qvbr7_360p_1000_qvbr7%2Fmord_mit_aussicht%2Fdash%2Fdash.mpd)) if required for further investigation.

Kind Regards,
Riva

Answer

Thank you for the provided insights :)

Answer

Hi Riva,

I looked at the DASH and HLS content. Both streams have identical sized segments (.ts for HLS and .mp4 for DASH) and amount to 4-5 Mbps average based on segment length. The reason you are seeing different bandwidth values in the player is most likely because the player is not calculating actual bitrate but showing whats indicated in the manifest.

For DASH it is picking the bandwidth attribute from the Representation tag

```

```
and for HLS it is picking the average bandwidth attribute

```
#EXT-X-STREAM-INF:BANDWIDTH=8350133,AVERAGE-BANDWIDTH=4952555,CODECS="avc1.640028,mp4a.40.2",RESOLUTION=1920x1080,FRAME-RATE=25.000,AUDIO="stereo"
```
As far as the actual segment bandwidth is concerned, it looks consistent between HLS and DASH.

| file                         | bandwidth |
|------------------------------|-----------|
| hlsvideo_1080_00002.ts       | 3.4MB     |
| hlsvideo_1080_00001.ts       | 5.4MB     |
| dashvideo_1080_000000002.mp4 |  3.3MB    |
| dashvideo_1080_000000001.mp4 | 5.3MB     |

file	bandwidth
hlsvideo_1080_00002.ts	3.4MB
hlsvideo_1080_00001.ts	5.4MB
dashvideo_1080_000000002.mp4	3.3MB
dashvideo_1080_000000001.mp4	5.3MB

Dash-Outputs with QVBR always exhaust the maximum bit rate allowed

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