Why Does iOS Video Streaming Suck? Part I

Experiment for you… Google for iphone youtube and look how pessimistic the completions are: the first is “iphone youtube fix” and the third is “iphone youtube not working”

Now do a search for iphone youtube slow and the completions all seem to tell a common story: that it’s slow on wifi. Moreover, there are more than 4 million hits across these search terms, with about 3.6 million just for “iphone youtube slow”.

Related searches show 630,000 hits for iphone netflix slow, 835,000 for iphone ustream slow and 9.6 million for the generic iphone video slow.

Surely something is going on.

I noticed it with my son’s YouTube habit. He often watches the various “let’s play” video game videos that people have posted, such as let’s play SSX. I keep hearing the audio start and stop, and realized that he keeps reaching the end of the buffer and starting over, just to hit the buffer again. Trying out YouTube myself, I find I often hit the same problem.

But when I was at CodeMash last week, even with a heavily loaded network, I was able to play YouTube and other videos on my iPhone and iPad much more consistently than I can at home. So this got me interested in figuring out what the problem is with my network.

Don’t get your hopes up… I haven’t figured it out. But I did manage to eliminate a lot of root causes, and make some interesting discoveries along the way.

The most common advice is to change your DNS server, usually to OpenDNS or Google Public DNS. Slow DNS is often the cause of web slowness, since many pages require lookups of many different sites for their various parts (images, ads, etc.). But this is less likely to be a problem for a pure video streaming app: you’re not hitting a bunch of different sites in the YouTube app, you’re presumably hitting the same YouTube content servers repeatedly. Moreover, I already had OpenDNS configured for my DNS lookups (which itself is a questionable practice, since it allegedly confuses Akamai).

Another suggestion that pops up in the forums is to selectively disable different bands from your wifi router. But there’s no consistency in the online advice as to whether b, g, or n is the most reliable, and dropping b and n from mine didn’t make a difference.

Furthermore, I have some old routers I need to put on craigslist, and I swapped them out to see if that would fix the problem. Replacing my D-Link DIR-644 with a Netgear WGR-614v4 or a Belkin “N Wireless Router” didn’t make a difference either.

In my testing, I focused on two sample videos, a YouTube video The Prom: Doomsday Theme from a 2008 symphonic performance of music from Doctor Who, and the Crunchyroll video The Melancholy of Haruhi Suzumiya Episode 3, played with the Crunchyroll iPhone app, so that I could try to expand the problem beyond the YouTube app and see if it applies to iOS video streaming in general.

And oh boy, does it ever. While the desktop versions of YouTube and Crunchyroll start immediately and play without pauses on my wifi laptop, their iOS equivalents are badly challenged to deliver even adequate performance. On my iPad, the “Doomsday” YouTube video takes at least 40 seconds to get enough video to start playing. Last night, it was nearly five minutes.

If anything, Crunchyroll performs worse on both iPhone and iPad. The “Haruhi” video starts almost immediately, but rarely gets more than a minute in before it exhausts the buffer and stops.

So what’s the problem? They’re all on the same network… but it turns out speeds are different. Using the website and the Mobile Speed Test app, I found that while my laptop gets 4.5 Mbps downstream at home, the iPad only gets about 2 Mbps, and the iPhone 3GS rarely gets over 1.5 Mbps.

I took the iPhone for a little tour to see if this was consistent on other networks, and got some odd results. Take a look at these:

The top two are on my LAN, and are pretty typical. The next two after that (1/22/11, 2:45 PM) are on the public wifi at the Meijer grocery/discount store in Cascade, MI. The two on the bottom are from a Culver’s restaurant just down 28th St. Two interesting points about these results. Again, neither gives me a download speed over 1.5 Mbps, but look at the uplink speed at Culver’s: 15 Mbps! Can this possibly be right? And if it is… why? Are the people who shoot straight-to-DVD movies in Grand Rapids coming over to Culver’s to upload their dailies while they enjoy a Value Basket?

As for Meijer, the ping and upload are dreadful… but it was the only place where Crunchyroll was actually able to keep up:

See that little white area on the scrubber just to the right of the playhead? It’s something I don’t see much on iOS: buffered data.

So what really is going on here anyways? For one thing, are we looking at progressive download or streaming? I suspect that both YouTube and Crunchyroll use HTTP Live Streaming. It’s easy to use with the iOS APIs, works with the codecs that are in the iDevices’ hardware, and optionally uses encryption (presumably any commercial service is going to need a DRM story in order to license commercial content). HLS can also automatically adjust to higher or lower bandwidth as conditions demand (well, it’s supposed to…). Furthermore, the App Store terms basically require the use of HLS for video streaming.

A look at the network traffic coming off the phone during a Crunchyroll session is instructive:

whois tells us that 65.49.43.x block is assigned to “CrunchyRoll, Inc.”, as expected, and it’s interesting to see that most of the traffic is on port 80 (which we’d expect from HLS), with the exception of one request on 443, which is presumably an https request. The fact that the phone keeps making new requests, rather than keeping one file connection open, is consistent with the workings of HLS, where the client downloads a .m3u8 playlist file, that simply provides a list of 30-second segment files that are then downloaded, queued, and played by the client. Given the consistent behavior between Crunchyroll and YouTube, and Apple’s emphasis on the technology, I’m inclined to hypothesize that we’re seeing HLS used by both apps.

But oh my goodness, why does it suck so much? The experience compares very poorly with YouTube on a laptop, which starts to play almost immediately and doesn’t stop after exhausting the buffer 30 seconds later. Whether you use Flash or the HTML5 support in YouTube (I’ve opted into the latter), it always just works, which is more than can currently be said of the iOS options, at least for me (and, if the Google hit count is right, for a couple million other people).

One other thing that doesn’t wash for me right now: remember when Apple started streaming their special events again? I blogged that it was a good demo of HLS, and I watched the first one with the iPhone, iPad, and Mac Pro running side-by-side to make a point that HLS was good stuff, and it all worked. How can the live stream hold up so well on three devices, yet a single archive stream falls apart on just one of the iOS devices?

I actually really like what I’ve seen of HLS: the spec is clean and the potential is immense. I even wondered aloud about doing a book on it eventually. But I can’t do that if I can’t get it working satisfactorily for myself.

What the hell is going on with this stuff?

If I ever get a good answer, there’ll be a “Part II”.

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Comments (5)

  1. jerbert

    I’ve noticed this lately, but on my MBP. The difference is that I’ve removed flash from it and so youtube is serving up straight h.264, just as it would to an iOS device. Now, I’ve had flash removed for quite a while but it’s only been in the last month that the slowdown has really kicked in.

    Videos on my mac are slow to start and I often have to pause them and wait for more to queue. Take the same exact youtube link over to Chrome on the same machine and it miraculously has NO problem.

    I’m not typically a tin foil hat kind of guy, but it does seem highly suspect that youtube, owned by google, maker of android, competitor of iOS, suddenly has problems serving up iOS specific videos.

    As a point of comparison I’m not seeing any of these slow videos from vimeo.

  2. Mashable has a good high-level overview of HTTP Live Streaming (and adaptive streaming protocols in general): Adaptive Bit Rate Video Streaming: Why Delivery Will Matter More Than Codec. Interesting that a third-party has made HLS available for Android.

  3. […] Now if Apple and the content providers could just work the kinks out… […]

  4. I have no idea if it’s related but Bob Cringley blogged about something he called Bufferbloat that supposedly reduces network performance the more buffers you have in between endpoints.

    Maybe something in iOS makes that worse.

  5. In fact, this problem goes even deeper. Remember, that the Apple TV 2 also uses iOS. Does this problem also occur there? Ohhhhh, yes, it does. And you know what? I’m using ETHERNET there! This problem has NOTHING to do with WiFi – if the iPhone had Ethernet, you’d see the problem there as well! I’ve been trying to track down this problem with my Apple TV, since I can’t stream anything over the very lowest quality YouTube video! Forget renting videos, and HD is a dream at the moment. My neighbor also has an Apple TV, but on the cable Internet product from the same company where I have my DSL, and his works like butter! I’ve tried messing with DNS servers, but that doesn’t seem to help the issue at all. Also tried changing routers, and even tried connecting to the DSL server with my Macbook Pro acting as the router, and nothing has changed the situation. The Apple forums are FULL of people with this problem on the Apple TV.

    Please keep looking into this – there HAS to be a solution!

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