Video decoding and display using the ffmpeg api and sdl api seem to be a bit technical. I recently received some emails asking about video decoding and display, today, hanyionet provides a blog article to briefly describe how to use these Apis. In fact, it is not difficult to use these Apis. Do not be afraid of complicated descriptions. All we need to do is first understand the process of video decoding and display, and then understand the role of each API. The reality of decoding and video is generally like this:
Initialization-> decoding-> image scaling-> video display
The following is a simple process flow chart, which provides some important APIs in each step. As you can see,The implementation of different steps is to find and use the corresponding API.
The API description in the figure is provided today.
FFmpeg API |
Description |
Av_register_all () |
Initializes libavformat and registers all the muxers, demuxers and protocols. |
Avcodec_find_decoder (...) |
Finds a decoder with a matching codec ID. |
Avcodec_alloc_context () |
Allocates an avcodeccontext and sets its fields to default values. |
Avcodec_alloc_frame () |
Allocates an avframe and sets its fields to default values. |
Sws_getcontext (...) |
Returns an swscontext to be used in sws_scale (). |
Sws_scale (...) |
Scales the data in source according to our settings in our swscontext C. srcstride and dststride are the Source and Destination linesize. |
Avcodec_decode_video (...) |
Decodes a video frame from buffer into picture. |
SDL API |
Description |
Sdl_setvideomode () |
Set up a video mode with the specified width, height, and bits-per-pixel. |
Sdl_createyuvoverlay () |
It is used to create a YUV overlay of the specified width, height and format for the provided display. |
Sdl_blitsurface () |
This performs a fast bits from the source surface to the destination surface. |
Sdl_freesurface () |
Frees (deletes) a SDL surface. |
Sdl_updaterect () |
Makes sure the given area is updated on the given screen. |
Sdl_flip () |
It is used to swap screen buffers. on hardware that supports double-buffering, this function sets up a flip and returns. |
Sdl_freeyuvoverlay () |
Free a YUV video overlay. |
In fact, to understand the ffmpeg api, another important thing is to understand the specific content of various data structures, such as avframe and avcodeccontext. I personally think these two structures are important.
After learning how to use these APIs, we should look for an example, such as ffplay. C or http://dranger.com/ffmpeg/. this example will be used, and the last example will be created based on this example.Video PlaybackProgram. Enjoy! This entry was posted in Streaming Media Technology (Hanyionet) |
