Real-time video encoding in DirectShow

Question

I have developed a Windows application that captures video from an external device using DirectShow. The image resolution is 640x480 and the videos saved without compression have very huge sizes (approx. 27MB per second).

My goal is to reduce this size as much as possible, so I am looking for an encoder which will allow me to compress the video in real-time. It could be H.264, MPEG-2 or anything else. It must allow me to save the video to disk and it would be best if I also could stream it in real-time over network (Wi-Fi, so the size should be around 1MB per second, or less). The significant quality loss would be unacceptable.

I have found out that getting an appropriate DirectShow filter for this task is very difficult. It can be assumed that the client machine is reasonably modern (fast 2-core CPU) and can utilize CUDA/OpenCL. There are a few apps that allow to encode video using CUDA and offer good performance, however I have not found an appropriate DirectShow filter or an API which could be used to develop one. The NVIDIA nvcuvenc.dll seems to have private API so I am unable to use it directly. Any CPU-based encoders I have found are too slow for my requirements, but maybe I have missed some.

Could anybody recommend me a solution, i.e. an encoder (paid or free, that can be used in an closed-source app) that can achieve a good performance, regardless whether it is using CPU/CUDA/OpenCL or DirectCompute? Or maybe I should use some external hardware video encoder?

Best regards,

madbadger

Answer 1

Forget about WMV encoding for realtime streaming. WMV works well for realtime low quality streams, but it doesn't do high quality encoding in realtime.

I suggest that you take a look at MainConcept's SDK. They do a series of DirectShow filters for encoding H.264. I've implemented realtime streaming and muxing of streams encoded in H.264 using MainConcept's codec and DirectShow filters, and it's great.

Hope this helps

Answer 2

See the CaptureDS C# sample that comes with AVBlocks. It shows how to build a video recorder with AVBlocks and DirectShow. DirectShow is used for video capture and AVBlocks is used for video encoding:

Answer 3

Here is one option : http://www.codeproject.com/Articles/421869/H-264-CUDA-Encoder-DirectShow-Filter-in-Csharp

It uses about 10% of my cpu (p4 3ghz) to encode a SD video to h264 in graph edit.

Answer 4

ffdshow tryouts leverage ffmpeg's x264 stuff, which is said to be pretty fast (I think so anyway). Also libjpeg-turbo might help, or choosing some other codec made for high throughput like camstudio's or what not.

update: ffmpeg can take directshow input now: http://ffmpeg.zeranoe.com/forum/viewtopic.php?f=3&t=27

Answer 5

Since you're using Directshow, by far the easiest thing to do would be to use WMV9 inside an ASF container. This is easier because it's available on almost all Windows machines (very few install time dependencies), decently fast (you should have no issues using it on a reasonably modern machine) and the quality is reasonable. But considering your limit is 8 mbit/sec (1 MB/sec), quality isn't an issue for you. 2 mbit/sec, VGA-resolution WMV9 should look quite good.

It's not nearly as good as a decent implementation of H264, but from an implementation standpoint, you're going to save yourself a lot of time by going this route.

See this:

http://msdn.microsoft.com/en-us/library/dd375008%28v=VS.85%29.aspx

Answer 6

I am using Windows Media Encoder for real-time encoding, and it works well even in resolution 720x576. One such example of it's usage is in VideoPhill Recorder.

It is written in pure .NET with DirectShow.NET for capturing and windowsMedia.NET for encoding.

Using those two I am able to achieve real-time encoding with 24/7 stability.

And both libraries are free to use on Windows, so you won't have to pay any licenses except for OS.