WiFi Bandwidth and Router considerations

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bhiga

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Oct 13, 2010
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Because Chromecast communicates solely via WiFi, the minimum sustained wireless bandwidth is critical for streaming quality.

This is usually not a problem for "normal" Chromecast applications that pull streams from the Internet - those services are designed to adapt to and scale with the available connection speed.

Content streaming from local devices is a different scenario altogether.

Chromecast doesn't necessarily work the same as traditional set-top media players (Apple TV, WDTV, Roku, etc) when streaming media from your phone/tablet/computer (device-local) and LAN-based (from a server) media can consume more bandwidth than you would expect.

Depending on where the media is located and how it is being sent to Chromecast, up to 3x the media's bitrate may be consumed (and required) on the WiFi network. If you have high bitrate media, this can easily overload an 802.11g connection or even an 802.11n connection.

Keep in mind that connection speed is not constant, and is limited by both your environment and your router.
Other nearby WiFi devices can cause interference, and the 2.4 GHz wireless band that Chromecast uses is "crowded" with many devices like cordless telephones and microwave ovens using overlapping frequencies.

Also, routers vary in the wireless speeds they can maintain. Just because you have a 802.11n 150 Mbps connection, that does not mean your router can truly sustain 150 Mbps throughput.

Better routers advertise use cases for "HD streaming" and have Gigabit LAN ports rather than 100 Mbps LAN ports found on cheaper models.
Just like a Gigabit Ethernet USB 2.0 adapter will never reach full Gigabit speed due the USB 2.0 bottleneck (480 Mbps), cheaper routers often are limited by their internal processor's lack of forwarding speed.

See the attachments for use examples and how the required bandwidth can multiply: Note that the 10 Mbps figure is just an example.
  1. Standard Internet stream example
    YouTube, Hulu Plus, HBO Go, VEVO, etc use this methodology
  2. Direct stream from LAN storage example
    Plex (from a local Plex server) and fling (from a desktop) work this way. Desktop and Tab casting from Chrome also uses this data flow.
    Data is sent from the LAN device via WiFi
    Chromecast receives data from the LAN device via WiFi
  3. Streaming from wireless device storage example
    Casting content stored on the device (device-local) from Avia or RealPlayer Cloud use this method.
    Data is sent from the casting device via WiFi to Chromecast
    Chromecast receives data via WiFi
  4. Forwarding from LAN storage example
    Casting content stored on a LAN device (DLNA, network share, etc) from Avia uses this method.
    Data is sent from the LAN device to casting device running Avia via WiFi
    Data is sent from the casting device running Avia via WiFi to Chromecast - this is the forwarding piece, data travels through
    Chromecast receives data via WiFi

To optimize available bandwidth for Chromecast:
  • Use an 802.11n dual-band router and put your other wireless devices on the 5 GHz access point whenever possible
    or use a separate WiFi access point connected to the wired network for Chromecast
  • Use wired connections for cast sources (server/desktop/laptop) wherever possible
  • Reencode high-bitrate media to lower bitrate (4 Mbps should be fine for most use)
  • Optimize Chromecast's ability to get a stable WiFi signal - move it away from the TV using the HDMI extender or an HDMI extension cable
    and/or move your router so it's closer to Chromecast (but not too close - too close can get into a "drowned in the noise" situation)
 

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stevewm

New member
Nov 6, 2010
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One big thing a lot of people don't realize is that wireless is half duplex...

If you have 2 devices on the same wireless network transferring data between each other, they will do so at half the speed, because only one device can talk at a time.

Say for example you have a PC wired to your router, and another PC on wireless.. You can copy a file between these computers at around 6MB/sec. Now you take the wired PC and connect it to the same wireless network instead. You will notice your copy speed is now around 3MB/sec.

If you are utilizing a wireless repeater to connect any of your devices to your wifi network, those connected to the repeater will experience the same halving of speed as well.

This is why having your local media source on a different band or wired helps so much.
 

sherdog16

Senior Member
Feb 9, 2012
298
96
One big thing a lot of people don't realize is that wireless is half duplex...

If you have 2 devices on the same wireless network transferring data between each other, they will do so at half the speed, because only one device can talk at a time.

Say for example you have a PC wired to your router, and another PC on wireless.. You can copy a file between these computers at around 6MB/sec. Now you take the wired PC and connect it to the same wireless network instead. You will notice your copy speed is now around 3MB/sec.

If you are utilizing a wireless repeater to connect any of your devices to your wifi network, those connected to the repeater will experience the same halving of speed as well.

This is why having your local media source on a different band or wired helps so much.

Here's a scenario I would appreciate your comment on:
I have a bridge that connects to my main router. The media source (laptop) is connected direct to the bridge which is in the living room with my CC, the CC is wireless to the bridge. Will the distance the bridge is from the main router come into play if doing local media?
 

rans0m00

Senior Member
Oct 11, 2012
376
60
Here's a scenario I would appreciate your comment on:
I have a bridge that connects to my main router. The media source (laptop) is connected direct to the bridge which is in the living room with my CC, the CC is wireless to the bridge. Will the distance the bridge is from the main router come into play if doing local media?

It shouldn't.... Unless the run to the main router is abnormally long.

My current setup has my plex server across the house from my TV room. Two out of three routers are upstairs and one is in the room with my plex server. All but one router is set up as access points. The distance combined between the three routers is roughly 200 feet. The distance is split between the three. Then roughly 25 feet from the closest router to the ccast. I have no more noticeable lag in the TV room than using the ccast in the back bedroom that the plex server is in.

I am sure if I was going to ping test this I would have a higher latency the further away it goes.... But like I said to real world use I can't tell it slows it down.

Sent from my Nexus 5 using Tapatalk
 

bhiga

Inactive Recognized Contributor
Oct 13, 2010
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I am sure if I was going to ping test this I would have a higher latency the further away it goes.... But like I said to real world use I can't tell it slows it down.
Exactly that. For home use, distance of wired connections doesn't matter much, as long as it's within specs and packets aren't being lost.

Distances for wireless connections, on the other hand, make a huge difference both in terms of latency and sustained transfer speed (bandwidth).
 
I've noticed that video casted from a tab is barely smooth at 480p. I am upstreaming at approx 150kbps.
When I try 720p, it struggles at 300kbps dropping to 150 alot. Using "extreme" it about the same rate but more choppy.

I have a N network with my laptop connected at 300M. I can usually transfer files around 3-6Mbps.

I'm a little confused why with chromcast, I can barely maintain 150kbps. Even if you multiply by 3, I'm not getting over 1mbps.
 

bhiga

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Oct 13, 2010
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I've noticed that video casted from a tab is barely smooth at 480p. I am upstreaming at approx 150kbps.
When I try 720p, it struggles at 300kbps dropping to 150 alot. Using "extreme" it about the same rate but more choppy.

I have a N network with my laptop connected at 300M. I can usually transfer files around 3-6Mbps.

I'm a little confused why with chromcast, I can barely maintain 150kbps. Even if you multiply by 3, I'm not getting over 1mbps.
It's likely not a wireless connection issue but rather a processing limitation on the computer you're casting from.

I just casted a 480p tab of full-tab video and my network utilization ranged from about 1.25 Mbps to bursts of 12 Mbps. The average was around 2-3 Mbps. What's the CPU utilization look like when you're casting?

Do other Chromecast apps like YouTube work okay with 720p or 1080p videos?
 
It's likely not a wireless connection issue but rather a processing limitation on the computer you're casting from.

I just casted a 480p tab of full-tab video and my network utilization ranged from about 1.25 Mbps to bursts of 12 Mbps. The average was around 2-3 Mbps. What's the CPU utilization look like when you're casting?

Do other Chromecast apps like YouTube work okay with 720p or 1080p videos?

CPU is an i5-2520M. Utilization is only around 20-30%. I've tried with and without Nvidia GPU.

Youtube seems ok at 720 and 1080, however, I thought that youtube videos get streamed directly to chromcast vs the laptop.
Also, when I stream a youtube video, I have no idea if chromecast sticks with my browser setting or figures out its own quality setting based on bandwidth. I thought it was the later.

Are you using regular Chrome, or Chrome Canary?
 

bhiga

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Oct 13, 2010
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CPU is an i5-2520M. Utilization is only around 20-30%. I've tried with and without Nvidia GPU.

Youtube seems ok at 720 and 1080, however, I thought that youtube videos get streamed directly to chromcast vs the laptop.
Also, when I stream a youtube video, I have no idea if chromecast sticks with my browser setting or figures out its own quality setting based on bandwidth. I thought it was the later.

Are you using regular Chrome, or Chrome Canary?
Interesting... You're correct that YouTube grabs the stream directly and determines the best settings. But if you have a 1080p TV and YouTube is pulling a 480p stream, it'll definitely be noticeable - especially on things like text.

My Chrome is Version 32.0.1700.107 m
and Google Cast Extension is 14.123.1.4

My system is relatively old, but it was a powerhouse in its day and still fine for what I do with it.
Windows 7 Professional 64-bit
Dual Quad-Core AMD Opteron 8389 2.9 GHz
32 GB RAM
AMD Radeon HD 7750​
 
Interesting... You're correct that YouTube grabs the stream directly and determines the best settings. But if you have a 1080p TV and YouTube is pulling a 480p stream, it'll definitely be noticeable - especially on things like text.

My Chrome is Version 32.0.1700.107 m
and Google Cast Extension is 14.123.1.4

My system is relatively old, but it was a powerhouse in its day and still fine for what I do with it.
Windows 7 Professional 64-bit
Dual Quad-Core AMD Opteron 8389 2.9 GHz
32 GB RAM
AMD Radeon HD 7750​

I'm running 35.0.1840.2 of Chrome and 14.123.1.5 of the extension.
I just tried installing regular chrome and had the same results.

your computer is def more powerful than mine, but I don't think thats the issue with such a low cpu utilization.
 

bhiga

Inactive Recognized Contributor
Oct 13, 2010
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I'm running 35.0.1840.2 of Chrome and 14.123.1.5 of the extension.
I just tried installing regular chrome and had the same results.

your computer is def more powerful than mine, but I don't think thats the issue with such a low cpu utilization.

Weird... do you have the Automatically resize the browser to best fit the receiver screen when casting a tab option enabled? That should provide lowest impact as it should eliminate the need to scale.

Does it make a difference if your laptop is plugged into wall power, or on a wired instead of wireless connection?
 
Weird... do you have the Automatically resize the browser to best fit the receiver screen when casting a tab option enabled? That should provide lowest impact as it should eliminate the need to scale.

Does it make a difference if your laptop is plugged into wall power, or on a wired instead of wireless connection?

ok, I just tried the wired connection and got some results. on 480p I got 150kbps, 720p got 300kbps, and extreme got around 600kbps.
720 and above started looking a little choppy. Picture Quality even at extreme was quite poor.
 

bhiga

Inactive Recognized Contributor
Oct 13, 2010
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ok, I just tried the wired connection and got some results. on 480p I got 150kbps, 720p got 300kbps, and extreme got around 600kbps.
720 and above started looking a little choppy. Picture Quality even at extreme was quite poor.
:( My CPU load jumps about 15-20% when casting too, so that seems in-line.

Weird, it's almost like something in Windows is throttling something...

You don't have some kind of third-party firewall or anything, do you?
If you're using the Windows Firewall, check the Advanced Settings for Inbound and Outbound rules on Wireless Portable Devices. My rules for those are disabled, but some folks have reported toggling them helped.
 
:( My CPU load jumps about 15-20% when casting too, so that seems in-line.

Weird, it's almost like something in Windows is throttling something...

You don't have some kind of third-party firewall or anything, do you?
If you're using the Windows Firewall, check the Advanced Settings for Inbound and Outbound rules on Wireless Portable Devices. My rules for those are disabled, but some folks have reported toggling them helped.

I have Avast which has some network protection
Tried toggling the settings in Windows firewall

I even tried disabling the firewall and anti-virus completely.

no difference
 

bhiga

Inactive Recognized Contributor
Oct 13, 2010
2,501
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I have Avast which has some network protection
Tried toggling the settings in Windows firewall

I even tried disabling the firewall and anti-virus completely.

no difference
Only other thing I can think of is to try unbinding Avast's network filter from the network interface (Properties the device itself and try un-checking any extra computer-looking icons) and trying it, often times disabling the firewall doesn't fully disable the network filter.
 
It's likely not a wireless connection issue but rather a processing limitation on the computer you're casting from.

I just casted a 480p tab of full-tab video and my network utilization ranged from about 1.25 Mbps to bursts of 12 Mbps. The average was around 2-3 Mbps. What's the CPU utilization look like when you're casting?

Do other Chromecast apps like YouTube work okay with 720p or 1080p videos?

Just to clarify, are you referring to BITS or BYTES?
I refer to bytes, 150kbytes/sec = approx 1mbit/sec
 

bhiga

Inactive Recognized Contributor
Oct 13, 2010
2,501
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well, even with bits, you're still faster than me.
I submitted a support ticket to google. still trying to get through the general "is it plugged in?" questions.
Yeah, it took me 2 or 3 rounds to get past the basics... Please keep us updated on what you find out.
 

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    Because Chromecast communicates solely via WiFi, the minimum sustained wireless bandwidth is critical for streaming quality.

    This is usually not a problem for "normal" Chromecast applications that pull streams from the Internet - those services are designed to adapt to and scale with the available connection speed.

    Content streaming from local devices is a different scenario altogether.

    Chromecast doesn't necessarily work the same as traditional set-top media players (Apple TV, WDTV, Roku, etc) when streaming media from your phone/tablet/computer (device-local) and LAN-based (from a server) media can consume more bandwidth than you would expect.

    Depending on where the media is located and how it is being sent to Chromecast, up to 3x the media's bitrate may be consumed (and required) on the WiFi network. If you have high bitrate media, this can easily overload an 802.11g connection or even an 802.11n connection.

    Keep in mind that connection speed is not constant, and is limited by both your environment and your router.
    Other nearby WiFi devices can cause interference, and the 2.4 GHz wireless band that Chromecast uses is "crowded" with many devices like cordless telephones and microwave ovens using overlapping frequencies.

    Also, routers vary in the wireless speeds they can maintain. Just because you have a 802.11n 150 Mbps connection, that does not mean your router can truly sustain 150 Mbps throughput.

    Better routers advertise use cases for "HD streaming" and have Gigabit LAN ports rather than 100 Mbps LAN ports found on cheaper models.
    Just like a Gigabit Ethernet USB 2.0 adapter will never reach full Gigabit speed due the USB 2.0 bottleneck (480 Mbps), cheaper routers often are limited by their internal processor's lack of forwarding speed.

    See the attachments for use examples and how the required bandwidth can multiply: Note that the 10 Mbps figure is just an example.
    1. Standard Internet stream example
      YouTube, Hulu Plus, HBO Go, VEVO, etc use this methodology
    2. Direct stream from LAN storage example
      Plex (from a local Plex server) and fling (from a desktop) work this way. Desktop and Tab casting from Chrome also uses this data flow.
      Data is sent from the LAN device via WiFi
      Chromecast receives data from the LAN device via WiFi
    3. Streaming from wireless device storage example
      Casting content stored on the device (device-local) from Avia or RealPlayer Cloud use this method.
      Data is sent from the casting device via WiFi to Chromecast
      Chromecast receives data via WiFi
    4. Forwarding from LAN storage example
      Casting content stored on a LAN device (DLNA, network share, etc) from Avia uses this method.
      Data is sent from the LAN device to casting device running Avia via WiFi
      Data is sent from the casting device running Avia via WiFi to Chromecast - this is the forwarding piece, data travels through
      Chromecast receives data via WiFi

    To optimize available bandwidth for Chromecast:
    • Use an 802.11n dual-band router and put your other wireless devices on the 5 GHz access point whenever possible
      or use a separate WiFi access point connected to the wired network for Chromecast
    • Use wired connections for cast sources (server/desktop/laptop) wherever possible
    • Reencode high-bitrate media to lower bitrate (4 Mbps should be fine for most use)
    • Optimize Chromecast's ability to get a stable WiFi signal - move it away from the TV using the HDMI extender or an HDMI extension cable
      and/or move your router so it's closer to Chromecast (but not too close - too close can get into a "drowned in the noise" situation)
    1
    Sounds like you're repeating the tests that many people have already done. Tab-casting is not perfectly smooth even on a very fast computer running at less than 12% CPU utilization in my experience. I would guess that the most likely explanation is a poor implementation in Google's "beta" code combined with too little buffering. You can easily see and hear that there is only a fraction of a second of buffering if the TV is in audio/video range of your computer. The video stream stutters and loses frames for an instant whenever Google's code can't keep up with a momentary increase in workload, even though the overall CPU utilization is low. Proper buffering should fix it, but Google hasn't seen fit to do that in the last 7 months.
    1
    bubbleguuum posted some some real-world experience and said essentially anything over 5 Mbit will be problematic, and most 1080p stuff is recorded at higher than 5 Mbit/sec.

    I now think that 5Mbps is a bit low. I think problems *can* definitely happen in the 8-20Mbps range, depending on the WiFi connection quality and its ability to sustain a stable bitrate.
    For reference, 1080p videos taken by the Nexus5 camera are about 17Mbps (close to 2 MB/s). I recorded such a video and one day it stuttered repeatedly, then the other day it played almost fine.
    WiFi is really hit and miss (often miss) for streaming high bitrate content.
    The problem with WiFi (vs wired) is that it is horribly bad at maintaining a stable high output bitrate: it can get high but it is very spiky and can get very low. Unlike Ethernet. This is really visible of you compared both with a network monitoring tool showing network bitrate output over time, streaming a high res video.
    1
    well my phone is a nexus 5 and has the fastest processor currently available and my router supports transfers up to 350Mbs on wireless N so i don't know what could be the issue. is everyone else able to stream from their device without stutter?

    I have some homework for you. I know this can be extremely frustrating. I've gone through it. Now Take 2 files, one that works fine and one that doesn't. Transfer them both to a pc. Right click--->properties--->details. Compare the two files. I would guess that the file(s) that doesn't work will have a much higher bit-rate.

    Despite what routers claim, and what the Chromecast claims, and what the guy at best buy claims, the numbers on the boxes aren't close to real world, sustained usage (it seems from my experience anyway). This is why the CC should have Ethernet. Period. And this is why Google doesn't officially support local video. If you want to cast your recorded vids, I suggest you run them through Handbrake with the settings I posted in the linked thread and they'll work. http://xdaforums.com/showthread.php?p=50682486#post50682486 Is that a pain in the balls? Yes. Was the Chromecast sold to you promising local video casting? No. Local video is something we're all trying to steal out of the device. Doing something with a device it wasn't designed for will ALWAYS come with hurdles and/or downfalls. It seems we all want our $35 apple tv ;)

    Edit:
    Suggestions other than Encoding:
    Put all media onto a lan connected device and/or have the CC connected to a router that nothing else uses which you connect to when you want to cast local media.
    Reason why:
    If you don't have any kind of media shaping or QoS (Quality of Service) set up, a router splits attention with all the devices that are talking to it. This means 5 devices and 2 way talking (phone to router--->router to CC) chop up that advertised 350mbps real quick (and like I said, that 350 is a peak theoretical value).

    Do keep in mind that this is all as i understand it...afaik
    1
    so i hooked up a toshiba USB hard drive to the router and put my media files onto it. using the bubbleupnp app i tried streaming from the hard drive to the cc. it does make an improvement but still choppy. the hard drive is hooked to the usb 3.0 port on the back of the router so i don't know what else i could do besides moving the tv into the room with the router and that isn't possible. guess i just have to wait until chromecast 2.0 comes out and hope they fix whatever is ailing it now. thanks for the help guys :)

    To address this bandwidth issue, the next version of BubbleUPnP will allow to specify a max bitrate that force transcoding if the original video is of a higer bitrate.
    For example, if you play a 1080p camera video whose bitrate is 18Mbps and you've specified a max bitrate of 10Mbps, it would be transcoded to a 10Mbps 720p video and play smoothly.