readme.md

Nim FFMpeg Binding (WIP)

(Very) Thin FFMpeg C binding for Nim. The thin binding means it's almost same with FFMpeg C APIs.
The advantage is that we can reuse our C APIs knowledge using Nim seamlessly. We can reuse any FFMpeg C tutorials to work with.

Examples

Some snippet here can be used to get the first 5 video frame

var frameCount = 0
while frameCount < 5:
    if av_read_frame(pFrameContext, pPacket) < 0: # negative means it's error
        continue                                  # and we just skip this time
    
    if packet[].stream_index == videoIndex:       # we only process packet in specific index stream
                                                  # in this case it's video stream
        if avcodec_send_packet(pVideoCodecCtx, pPacket) < 0:  # negative means it's error
            continue
        if avcodec_receive_frame(pVideoCodecCtx, pFrame) < 0:
            continue
        doSomethingWith3YUVPlaneData(pFrame[].data) # pFrame[].data is array filled with YUV several planes
                                                    # pFrame[].data[0] is Y plane
                                                    # pFrame[].data[1] is U plane (or Cb be precise)
                                                    # pFrame[].data[2] is V plane (or Cr be precise)
        inc frameCount

Snippet to get the first video stream index

var videoIndex = -1
var streams = cast[ptr UncheckedArray[ptr AVStream]](pFormatCtx[].streams)
for i in 0 .. pFormatCtx[].nb_streams:
  let localparam = streams[i][].codecpar
  if localparam[].codec_type == AVMEDIA_TYPE_VIDEO:
    videoIndex = int i
    break

The index can be used later to know which stream index packet we'll process later.

Any others examples you found should be applicable with this binding too. Several worked examples also availables in examples folder.

To use

To able to compile and work with, make sure we installed shared lib to run it.