Leading up to the Sling launch, there was lots of question about how the quality on Sling would be. In a reddit AMA before the beta started, Roger Lynch confirmed that Sling would offer 1080p video and 5.1 surround sound. Now that Sling has launched, many have been a little disappointed by the quality of the service. While it's certainly not bad quality, it doesn't seem to be up to the standard they were pitching either. Being curious, and knowing just enough about computers to be dangerous, I decided to see if I could figure out the technical specs of their streams...
Note: Before we begin, let me explain that I determined all this by packet sniffing the PC client. Different clients may have different streams available to them, but I doubt that, at least at present time. Also, before you get excited, the streams are all encrypted to prevent people from dumping them. You are able to pull the metadata off of them but you can't use this method to save the video.
Sling TV Stream Details
First off, I found out that the streams were of differing quality depending on what channel you were watching. Sling has apparently tailored different encoding profiles to different types of content which is nice. They also are using x264 for video encoding, which I did not expect.
Sadly, my suspicions were confirmed, Sling (at least for the PC client) is not offering 1080p and surround sound. It seems to top off at 720p and is always only stereo.
Below I have listed the encoding profile that each channel is using. As you are probably aware, they are adaptive quality and jump between various qualities depending on how much bandwidth is available at any given time. For simplicity sake, I've only listed the highest quality available for each channel. If you're curious about the other qualities, ask in the comments. Each channel has about 10 different streams available to it, so there's certainly lots of wiggle room.
ESPN 1 & 2
- Resolution: 1216 x 684
- Framerate: 59.94fps
- Target Bitrate: 4.5Mbps
- Profile: Level 4.0 High
- Reference frames: 4
- B frames: 3
- CABAC: yes
- x264 Preset: Medium
- x264 Tune: Film
- Audio: 192kbps 48KHz stereo AAC
TNT, TBS, HGTV, Food, Travel, CNN, CN/AS, ABC Family, Galavision
- Resolution: 1280 x 720
- Framerate: 29.97fps
- Target Bitrate: 3.5Mbps
- Profile: Level 4.0 High
- Reference frames: 4
- B frames: 3
- CABAC: yes
- x264 Preset: Slow
- x264 Tune: Film
- Audio: 192kbps 48KHz stereo AAC
El Ray
- Resolution: 480 x 480
- Framerate: 29.97fps
- Target Bitrate: 1.8Mbps
- Profile: Level 3.1 Main
- Reference frames: 5
- B frames: 3
- CABAC: yes
- x264 Preset: Medium
- x264 Tune: Film
- Audio: 160kbps 48KHz stereo AAC
Strangely, Maker and Disney seem to be using a different protocol than the rest of the channels. Rather than make assumptions on their quality, I'll just leave them as unknown at this point.
I'll update this post if I am able to figure out more, but I figured people would be interested in my findings thus far.