Is it possible to generate video at 60 fps and play it back at 60 fps?

For a high-perfor开发者_运维技巧mance scientific purpose we need to render video and play it at 60fps on the device. I assume the usual frame rate of H.264 video is lower than that.

Is this possible, or is the framerate fixed? If so, what is the maximum frame rate we can get when playing H.264 video in fullscreen on the device?

---

Technical specifications will vary from iOS device to iOS device, so you'll need to check for the hardware you'll actually run this on. For the iPad 2, currently the most powerful of the iOS devices, Apple's technical specifications for video list the following:

Video formats supported: H.264 video up to 720p, 30 frames per second, Main Profile level 3.1 with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; MPEG-4 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple Profile with AAC-LC audio up to 160 Kbps per channel, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; Motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 720 pixels, 30 frames per second, audio in ulaw, PCM stereo audio in .avi file format

It would appear that fullscreen H.264 playback at 60 FPS is not supported on even the robust hardware of the iPad 2.

However, you can indeed render content to the screen at 60 FPS. I do this all the time in both Core Animation heavy applications and ones that use OpenGL ES. If you can generate your content in-application fast enough to display at this rate, you could render it to the screen at 60 FPS, then encode every other frame to video.

Given that video encoding is a reasonably expensive operation, and it sounds like you want to run some kind of simulation here as well, I'm guessing that you won't be able to render each frame at 60 FPS for display to the screen on current hardware simply due to the load you'll put on the system.

---

Yes, it is possible to encode video as a series of images and then display the images very quickly on screen. The upper limit of the video hardware and the time to decode the images and blit the images into the video card are the bottleneck in this process. As long as your image decoding logic is not too slow, it should be possible to push video data to the graphics card at 60FPS.

You could try to implement this yourself with a series of PNG images, but I think you will find that decoding the PNG image will not be fast enough to get 60 FPS playback. You can find some free example code that implements that approach with PNG images in my answer to this question

If you cannot get the performance you need, then take a look at my AVAnimator library for iOS, as it already fully solves this problem using memory mapped frames that can be sent directly to the video card from mapped memory.