Project Rémoulade

DivX H.264 Encoder Alpha 1

The second package to be released from Project Rémoulade is an alpha version of the DivX H.264 Encoder. Complementing the DivX H.264 Decoder, this multithreaded encoder produces high definition H.264 video bitstreams that are compatible with the draft profile for DivX 7 H.264 HD video. The encoder is a command line utility and accepts input from raw AVI files as well as the AVISynth frameserver.

View our tutorial for the DivX H.264 Encoder

DivX H.264 Decoder Beta 2

Beta 2 is here!

Thanks to a wealth of feedback since our first beta release last week, we have already completed work on many improvements to the decoder and still more are underway. Once again, we ask for your help testing and we look forward to seeing more of your results

What's new in Beta 2

The following changes have been made to the decoder:

• The preferred output format has been changed to YV12 and, used in conjunction with renderers that accept this format, decoding should be faster
• More routines have been implemented in SSE for acceleration on older processors
• An issue causing high jitter on certain clips has been corrected
• Experimental support for "old-style" lossless bitstreams has been added
• Multithreading code has been adapted to address infrequent crashes
• CABAC decoding has improved error resilience
  

Known-issues for Beta 2

This non-exhaustive list of known-issues summarizes some important points you should be aware of when using Beta 2:

• The decoder does not perform as well as expected when running on AMD CPUs (we are actively investigating this issue)
• DVBViewer crashes if the DivX H.264 Decoder is selected for live streams.

DivX H.264 Decoder Beta 1

Our first release from Project Rémoulade is a beta version of the DivX H.264 decoder. It is a multithreaded DirectShow filter supporting high profile bitstreams and is capable of decoding all streams from the current version of x264 with incredible playback performance.

Features of the DivX H.264 Decoder

Configuring the decoder

Once installed the decoder can be configured either by accessing the filter property page from a host application (i.e. a media player), or by selecting the H.264 Decoder Config link in the DivX programs group on your Start menu:

Click to enlarge

The options that can be set include:

Creating our test clips

To test the new decoder we encoded a 12 minute long video sequence from Last Man Standing, a very sharp source clip combining high texture detail, fast motion, strong color contrast, flashing lights, frequent scene changes, computer graphics, indoor and outdoor scenes, and smoke and particles. It was encoded using x264 version 0.59.807 08b5132 with the following options:

We ran one encoding using --qp 16, resulting in output with an average data rate of 45.57Mbps, and another with --bitrate 15000 --pass <1,2>. The 45 Mbps stream is extremely high quality and the high data rate ensures that during benchmarks the majority of the CPU time is spent in the decoder (as opposed to the file splitter, renderer, or host application). The 15 Mbps stream represents a rate more typical of common 1080p material.

Our test clips are too large to post but you can view some representative sample images:

Click to view slideshow

Results of our own initial testing

In order to provide some insight into Beta 1 we ran a few benchmarks against some mature third-party H.264 decoder filters, namely CoreAVC 1.7.0 and FFDShow-tryouts rev 1945 CLSID build, dated 2008-04-17. For each decoder we used GraphEdit to create a filter graph comprising the Haali splitter, the H.264 decoder and the default video renderer filter. The graph configuration looked like this:

Click to enlarge

We disabled the clock for the graph, displayed the properties for the renderer filter, used Process Explorer to measure the total CPU time required to decode each clip subtracting any CPU time accumulated until the graph was run, and also noted the average frames per second achieved. We decoded each clip with every decoder three times for all of our dual core benchmarks but only twice for our single CPU benchmarks because these take much longer and the dual core tests had showed almost no deviation across multiple repetitions for any decoder on our test machine. For fairness, for every decoder we chose the result with the highest average frame rate per second of CPU time.

Our test system used an Intel Core 2 Extreme X6800 (Conroe) CPU @ 2.93Ghz, 1066Mhz FSB, 4MB of L2 cache, 4GB of DDR2 RAM, and a PCI-Express NVIDIA Quadro FX 3550/4000 SDI video card with 256MB of memory, a 256-bit bus, and ForceWare version 6.14.11.6265.

Click to enlarge

To begin, these charts show the average frames per second per decoder according to the renderer filter:

Click to view charts

You can see that on our test system Beta 1 already achieves far more frames per second (average) than FFDShow-tryouts, and also bests CoreAVC in three out of four cases. But how much CPU time was used by each decoder to obtain these results? A fast decoder is not necessarily performing well if it consumes too much CPU time. To further investigate the performance of each decoder we also charted the total CPU time used in each case:

Click to view charts

Once again the decoder performs extremely well for it's first beta release! The charts clearly show that the DivX H.264 decoder is not simply achieving high frame rates at the expense of excessive CPU time. Performance will be further enhanced as we roll out more beta releases at DivX Labs. Stay tuned ;)

An update on performance

Since releasing Beta 1 we have gathered a lot of information from members of the beta group including performance statistics for many more CPU types. Although we can consistently reproduce the above illustrated performance on our test system which was not specially selected, proving the high efficiency of the decoder core, third-party performance tests on other processors have shown some variance - particularly those performed with CPUs that have less L2 cache. This is somewhat expected as early versions of the decoder are tested for the first time on a wider range of hardware and the current beta version generally performs to within 10% of the frame rate achieved by CoreAVC on the same system. We are actively working to ensure that the decoder performs equally well across all common processor configurations.

Downloading DivX H.264 Decoder Beta 1

This is a closed beta release and our beta group has limited capacity. We are now making efforts to contact active members of the video community with invitations, as well as developers and enthusiasts who might help us with testing and provide feedback. If you believe that you fall into these categories and you are interested in testing this beta please create a free DivX Labs account and send me a private message including your preferred e-mail address and a short summary of any relevant projects or groups that you are involved with. Please be patient when applying, we will try to respond quickly but we're only human and we too need our beauty sleep ;)