Netflix – meditations on a video streaming giant

18 July 2012 7 comments

Netflix, during June, reached the record level of 1 Billion hours streamed in a month. It is an incredibly huge level of bandwidth, an impetuous and growing stream of bits that makes Netflix one of the TOP10 Internet bandwidth “consumer”. But how much does it cost to Netflix this huge stream ?

I remember an article of a couple years ago by Dan Rayburn in which he estimated an average cost of 3c$ per GByte, a low rate usually applied by CDNs to very large clients. In an article of 2011, Dan corrected the estimation discussing a more complex pricing model for such big players (a mix of per GB and per Gbit/s). The new estimation can, however, be approximated to 1.5c$/GB.

This level of pricing may seem very low and negligible in the overall Netflix’s business, but I think that the growing consumption due to the relatively high average of content streamed per user per month may be a problem for Netflix if not brought under control.

Let’s dig deeper in the numbers.

Let’s suppose that the average bitrate streamed to users is 2.4 Mbit/s (see this post in the netflix blog), this means that every hour of content requires in average 1080 MB (1GB).

If you multiply this for 1Billion hours you have 1 Billion GBs * 1.5c$ = 10M$ / month, 120 M$ per year.

Compared to the cost of CDNs of 2011, 2012 is around the double. This is caused by an increase in the number of clients but most of all by an increase in the average amount of data streamed per client. A wopping 90 minutes per day per user. I think that this may be considered near the maximum possible but a further increase to 120 minutes may be realistic in a worst case simulation. This would mean 160M$ per year.

With these premises it is not a surprise that Netflix is searching to control delivery costs creating their own, single purpose, CDN and optimizing encoding.

You know that I’m very sensible to encoding optimization. I have always stated that for this kind of business encoding optimization is of fundamental importance. I have already demostrated in the past that H.264 can be optimized much more then what players like Youtube, Netflix, Hulu, BBC  are doing today. Here I specifically addressed Youtube and Netflix.

Netflix could benefits of a 30% to 50% reduction in average bitrate consumption with a strong optimization of the entire encoding pipeline (plus eventually of the Silverlight player). This could mean savings for 60-80M$ per year and at the same time an improvement in the average quality delivered to client, a key feature in the increasingly competitive market of OTT video.

Categories: Video

FFmpeg – the swiss army knife of Internet Streaming – part V

2 July 2012 29 comments


PART I – Introduction (revised 02-jul-2012)
PART II – Parameters and recipes (revised 02-jul-2012)
PART III – Encoding in H.264 (revised 02-jul-2012)
PART IV – FFmpeg for streaming (revised 02-jul-2012)
PART V – Advanced usage (revised, 19-oct-2012)
PART VI – Filtering (new, 19-oct-2012)


After almost one year from the starting post of this series dedicated to FFmpeg I have found some time to catch-up with this topic and revise/refresh the series. In this year a lot of things happened on the FFmpeg side (and not only), so I have corrected a lot of small errors and changes in syntax of commonly used commands. So this is also a good opportunity for you to refresh your knowledge about FFmpeg and the current state-of-the-art. Above you find the Index of the articles.

The most important changes are around parameters like -vcodec, -b, -ab, -vframes, etc… to avoid misunderstandings now a stream_identifier has been added to specify if the parameter is related to the audio or video track. In case of multiple AV tracks there also an optiona parameter to specify the track number. Take a look at the updates of PART II to have more informations about new syntax and obsolete parameters.

Another important change is realated to libfaac library which is now external. Read point 2 below to know about alternatives.

Last but not least, FFmpeg introduced the possibility to control directly the parameters of x264lib using the -x264opts command. Not for everyone but very useful when you want the control and performance of x264 and all the input and output options of FFmpeg.

Fifth Part – Advanced Usage

This fifth article wants to add more advanced use cases and usages to what was presented and discussed in the previous 4 parts. This article will be enriched in the next weeks and months to include even more advanced examples and use cases that can be solved with a smart use of FFmpeg. Good reading!

1. Optimize multi-pass multi-bitrates encoding

You know that encoding for dynamic streaming techniques (HDS, HLS, Silverlight) requires the renditions to have aligned keyframes and be CBR or capped VBR.
A neat trick to avoid the limit of fixed length GOPs is to assure a consistent alignment of keyframes across renditions reusing the same first pass statfile across renditions.

ffmpeg –i IN –pass 1 –an –vcodec libx264 –r 30 –b 1500k –bufsize 1500k –keyint_min 60 –g 120 –s 1280×720 –vpre slower_fastfirstpass OUT_1500.mp4

This command line is the first pass of the first rendition. The first pass generates a stat file for the second pass.

ffmpeg –i IN –pass 2 –an –vcodec libx264 –r 30 –b 1500k –bufsize 1500k –keyint_min 60 –g 120 –s 1280×720 –vpre slower OUT_1500.mp4

Instead of recreating a first pass stat file for the next renditions, you can use the previous simply launching the second passes of the next renditions

ffmpeg –i IN –pass 2 –an –vcodec libx264 –r 30 –b 1000k –bufsize 1000k –keyint_min 60 –g 120 –s 854×480 –vpre slower O_1000.mp4
ffmpeg –i IN –pass 2 –an –vcodec libx264 –r 30 –b 500k –bufsize 500k –keyint_min 60 –g 120 –s 640×360 –vpre slower O_500.mp4

Since the second pass is less accurate if it use a stat file generated with a too much different resolution and bitrate, may be better to use a rendition in the middle to generate the first pass and not the highest rendition.

2. AAC encoding

libfaac has been extracted from ffmpeg and is now an external library. There are two alternatives yet embedded inside ffmpeg: libvo_aacenc or the standard aac library.

ffmpeg input.mp3 -c:a libvo_aacenc -b:a 96k -ac 2 -ar 44100 output.aac

ffmpeg input.mp3 -c:a aac -strict experimental -b:a 96k -ac 2 -ar 44100 output.aac

I have tested both and it seems to me that libvo is the best alternative. It produces a sufficiently good AAC LC.
In a future article I’ll explore some alternative like encoding audio track externally and remux then with ffmpeg or mp4box.
This is a must go if you need the higher efficiency of HE AAC or HE AAC v2.

3. Joining video

Joining video is strangely a complex task with FFmpeg. A reader suggested this solution (via Steven’s Blog):

ffmpeg -ss 100 -t 10 -i in.mp4 -c copy -bsf h264_mp4toannexb 100.h264
ffmpeg -ss 200 -t 10 -i in.mp4 -c copy -bsf h264_mp4toannexb 200.h264
ffmpeg -i concat:”100.h264|200.h264″ -i in.mp3 -c copy out.mp4
The first two lines generate two h.264 elementary streams. The h264_mp4toannexb option is mandatory to be able to concatenate efficiently elementary streams at binary level.
The third line use the concat option to cancatenate the ES segments to form a new input.
I usually use mp4box for this kind of purpose and not FFmpeg.

4. Use an HLS stream as source

FFmpeg now supports also Apple HTTP Live Streaming as an input protocol. So it is really simple to acquire or repurpose an HLS streaming, simply specify the path to .m3u8 manifest.

ES: Do you want to stream an existing .m3u8 stream to Flash on the desktop using FMS (now AMS) ? Try this:
ffmpeg -re -i http://server/path/stream.m3u8 -c copy -f flv "rtmp://FMSserver/app/streamName live=1"

5. Record a stream endlessly rotating target file

Segmenting feature of FFmpeg can also be useful to create an endless recorder with rotating buffer. It can be done using the segment_wrap parameter that wraps around segment index once it reached a limit.

ffmpeg -i rtmp://INPUT -codec copy -f segment -segment_list out.list -segment_time 3600 -segment_wrap 24 out%03d.mp4
The previous commandline records endlessly the INPUT stream in a ring buffer formed by 24 chunk of 1hr video.Conclusionfollow me on twitter to know more about FFmpeg and video related topics (@sonnati).


PART I – Introduction (revised 02-jul-2012)
PART II – Parameters and recipes (revised 02-jul-2012)
PART III – Encoding in H.264 (revised 02-jul-2012)
PART IV – FFmpeg for streaming (revised 02-jul-2012)
PART V – Advanced usage (revised, 19-oct-2012)
PART VI – Filtering (new, 19-oct-2012)


Categories: Video

Adobe Media Server 5 announced

23 May 2012 5 comments

Adobe has announced that the new Adobe Media Server 5 (formerly Flash Media Server) will be available soon. The change in the name reflects the recent shift in strategy of Adobe [sarcastic mode on] that is running away from Flash as fast as possible to embrace more cool technolgies like, in this case, HLS [sarcastic mode off].

Irony apart, I’m very happy with this announcement because I have always stated that FMS could have interesting new possibilities supporting streaming for iOS with content protection. FMS supports HLS streaming since release 4.5, but this is not sufficient to keep the leadership.

I work for large media clients that need content protection and in the last 2 years I have seen such clients choose MS’s SmoothStreaming and PlayReady too much times because some independent vendors have been able to offer them native clients for iOS supporting PlayReady DRM inside HLS protocol.
So it’s impossible to remain on the technology and adoption edge if not supporting all the business needs for the most preminent mobile platform.

Now with AMS 5 we are able to use our preferite streaming server to deliver protected content to iOS device too, both in applications created with AIR as well as native ObjC apps.

We have two protection techniques: full blown DRM protection using Adobe Access 4 (again “Flash” is flashed away) or using PHLS (Protected HLS) the HLS version of PHDS (Protected Http Dynamic Streaming).

This last feature is indeed very interesting because offers a stronger protection than the very simple encryption possible with standard HLS without requiring the costs and worries of DRM servers.

More info in the Kevin Towes’ Blog

Categories: AMS, FMS

Market repositioning of Flash begins (updated)

1 March 2012 3 comments

I have already talked (perhaps too much) about the Future of Flash in this post. There I didn’t hide my perplexities about the Market position of Flash compared to alternative technologies. After the drop of Flash Player for Mobile there was a strong decline in confidence for Flash platform. But now the scenario is beginning to emerge sharply and I begin to understand the purpose of the Adobe strategy.

Yesterday Adobe has released a public beta of AIR 3.2 for mobile application development. This version implement the promised support for Stage3D in mobile platforms like iOS and Android. A number of demo video appeared on the web showing excellent 3D performance and a lot of renewed interest about mobile game development using  AIR:

Square Enix’s [Barts] running on Android

The time will tell, but AIR has the potentialities to become a leader platform in 2D/3D games development. A single code base is sufficient to create a game for Desktop (AIR’s captivate runtime), Browser (someone named Facebook ?) and now iOS and Android. With ConnectedTVs and STBs support to come (already showed during MAX), the dream of the Open Screen project is becoming reality, at least in the game dev area (but also intensive graphic/media applications may leverage 2D/3D accelerations).

Therefore Adobe has concentrated the resources in a promising field where Flash could easily become leader. In 2D/3D browser gaming it is just leader (500Million players on Facebook may be sufficient as business card ?) . Try by yourself searching for Stage3D demo in YouTube to see the huge amount of interest for this technology from any game developers (big and small).

The second strong commitment of the platform is for video delivery where Flash has been leader in the past 5 years and is still today. The performance of video decoding in the browser has been widely improved with a completely redesigned pipeline that now exploits mult-threading heavily. But most important, the support for accelerated H.264 streaming has been added to AIR for iOS using the standard Apple HLS (already supported by FMS 4.5 and Wowza Server).

During the spring Adobe will release the new version of Flash Access (now Adobe Access 4) that will include content protection for iOS devices (both in AIR and native application) in the form of DRM on HLS. This move has the potentiality to make Adobe re-gain the favor of majors and big content providers that would have the possibility to uniform DRMs across Android, iOS, Desktop Apps, Browsers, Google TV and some STBs.

The support for HW accelerated 2D, 3D and video playback on mobile, plus an improvement in performance for Flex applications, plus the possibility to integrate HTML5 contents with StageWebView, plus the DRM, plus native extentions, **finally**, makes AIR (for Mobile) an interesting, efficient, effective and valuable solution for cross platform application development.

(Updated 03 March 2012)

I think the platform is 99% complete now, which is very good, but I would like to see the following issues addressed ASAP to complete the features list of AIR for Mobile:

  • H.264/AAC on RTMP : necessary for effecient real time video application, especially now that FP supports H.264 encoding.
  • Echo cancellation : see the previous point.
  • Effective and Robust support for key native features like InApp Purchase and Notification. I like Native Extentions’s idea but I’d prefer an official API for critical features like these.
  • Better integration/communication between AS3 and JS in StageWebView. No more hacks please.

Make a comment if you think that there’s something else of important to add to AIR for Mobile/AIR for iOS.

Categories: Flash, Mobile, Video

What about the future of Flash ?

16 January 2012 8 comments

Long time passed since my last post on this blog. I have been very busy in an important video streaming project but this is not the only reason for my absence. I have also wanted to wait and take all the necessary time to analyze, ponder and “digest” the infamous Flash affair.
I will not hide my bitterness about the fact, but I’m also more optimitic now, after I have seen the real consequences and have had the time to elaborate on the future scenario. I’ts not all a bed of roses but I’m somewhat optimistic.

First of all, fortunately, I’m not limited to Flash technology in my consultancies. I work with .net technologies for many years and I have designed and deployed successful streaming services in HLS with both Wowza Server and FMS 4.5

You also know that I’m an encoding expert with important success cases and a deep knowledge of commercial and open source encoders like Ffmpeg, x264, Flip Factory, Telestream Vantage, Atheme KFE, Rozhet CarbonCoder, Digital Rapids to name a few.

I have created encoding pipelines and optimized existing ones for delivery platforms based on HLS, Flash HDS, MS Silverlight and ipTV and designed decoding and delivery optimizations for Flash and Silverlight.

So when I talk about my bitterness, it is not driven by the fear for the future but by the awareness of the big mistake that Adobe has done stabbing Flash in the back. I want to focus this post on the future prospectives for Flash and not on the disastrous announcement of Adobe (a masterpiece of masochism, at least from a PR point of view), however a brief summary of my thoughts on the topic is a good thing. I do two short considerations:

1. Adobe may also have had good, long term stategic reasons for dropping Flash for mobile browser, but they could choose modes and terms with much less collateral damages. Why not reduce progressively the commitments and the investments across the lifespan of FP11 to avoid harming the Flash Community ? After all, FP11 has been released for Android and QNX and it has brought important improvements in performance and stability. I know that Flash for mobile browsing has a lot of problems and those problems are due tot the excessive use of bad Flash coding that has been done over  time especially for advertising. Obviously if you have a page with 5-6 Flash banners that can kill an old desktop computer, how can be able a tablet to handle this ?
A simple solution could be to put every swf  of a page in an idle mode, with a clickable poster image that activates the swf  only when touched. Simple, clear and always better than have no Flash support in mobile browsing.

2. Adobe just does not realize that is killing the goose that lays golden eggs. Have you even thought about the fact that Flash is used every day by 2 billion people! It’s probably the most pervasive peace of sofware after MS Windows. Giants like Steve Jobs would have exploited such competitive advantage in ways that the current Adobe management are not even able to imagine. Yet it is not difficult to imagine for example a marketplace of Flash and AIR apps on the model of the MacOS AppStore (but with 20 times more potential customers). What it is worth this kind of power ? Evidently near t0 zero for Adobe.

But now the damage is done and it worth nothing to complain, and so there will be some short, medium and long term consequences. The short term consequences are paradoxically positive for experienced Flash developers. This is because new developers, creative shops and consultancy firms are focusing interest to HTML5 because of the bad medium and long term outlook for the Flash technology and because of  marketing reasons. But the demand for Flash technology is not decrasing as fast as the offer and so there is a burst in the amount of work available for skilled developers.

In a medium term I see an higher convergence between the demand and offer for Flash-based projects in general. Flash will mainain or increase it’s penetration in web gaming thanks to 3D (remember that the casual game market on Internet is completely Flash-centric today, how forget that every day 200+ million people play some Flash games in Facebook ?) and probably will remain the reference for video streaming, but in the RIA market and creative market HTML5 will definitely gain it’s momentum (in real terms, not like now where only a few important creative, video or gaming projects has migrated from Flash to HTML5).

Flash in the mobile market, as a cross platform mobile development technology, has not, in my opinion a clear outlook for the future.  The sudden drop of Flash for mobile browser and the drastic reduction of commitment for Flex has been percepited as a treachery of Adobe from the point of view of the loyal base of sustainers and developers and as a definitive change in the wind from the point of view of customers and stake holders. How to blame them ? the lack of support from its own creator is a mortal stub for a technology and the message from Adobe is clear: in the long term we’ll substitute Flash with HTML5. Not only, we will focus more on tools than technologies (Flex docet).

No place for developers in the future of Adobe ? I don’t know but the long term perspective of Flash, Flex and other Flash related technology (FMS?) has been heavely perturbated by the infamous move. Flex is now an Apache baked project but is it a guarantee of evolution and support ? Who will invest time and credibility among customers in a technology for mobile development that has not a clear commitment from its creator and controller ?

Concluding, what I intends to do as a Flash developer ? In the short term I have to do a lot of Flash related projects, so no problem. In the medium term I think to continue using Flash/AIR for Mobile development. This is a clear path for me, I can capitalize on my AS3,Flash and Flex platform skills to develop desktop, browser and mobile apps. Now the level of features for Android and iOS has become good enough to be able to develop any kind of apps without the need for adding Java and Objective C to your skill portfolio (in my opinion, the recent support for notifications, in app purchase and HLS have cleared the top three entries of the most wanted and needed features list).

And in the long-term ? I dont’ have an answer, I think I’ll simply wait and see.

PS: Very interesting article about “migrating” from Flex to JS (Thanks to Anna Karim) –

Categories: Flash, Mobile, Video

My presentation at MAX2011 is available on Adobe TV

10 October 2011 5 comments

Finally the recording of my presentation at MAX2011 (Encoding for performance on multiple devices) is available on Adobe TV.

You can also download the pdf version here. My using of FFmpeg for repurposing the streams of FMS has attracted quite a lot of interest and attention. I’m planning to extend the series of article dedicated to FFmpeg and also to transform it in a permanent knowledge-base on FFmpeg and related best-practices.

Categories: Flash, FMS, Video

New apps for Playbook: Virgin, RMC and 105 Radio XL and TV

2 October 2011 2 comments

Finally the applications I have developed with Flex and AIR for Playbook are officially in the RIM AppWorld market.
They are 6 media apps developed for Finelco, the owner of the biggest radio network in Italy.

The first 3 are dedicated to 5 music web TV channels (app names : Radio 105 TV, Radio Monte Carlo TV, Virgin Radio TV).  
The other 3 offer a complete multimedia experience with:

– A selection of thematic web radio plus the live broadcast of the main radio channel
– A selection of podcasts (MP3) from the main programs of the radio
– The charts/playlist created by the sound designers or voted by the users
– A multi-touch photo gallery
– A selection of VOD contents like video clips, interviews, concerts

(App names: Radio 105 XL, Radio Monte Carlo XL, Virgin Radio XL).

I’m very proud because the apps are collecting a lot of 5 starts reviews. Flex and AIR can assure an excellent UX, especially for multimedia (live audio, live video, vod and so on), and a easy customization.

Pictures from the Virgin Radio app:

If you have not a Playbook, take a look at the UX in this video:

Categories: Mobile

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