How to use ffmpeg to convert and display video in Python (Windows)?

The following prorgram shows how to feed data into FFMPEG and get data from FFMPEG and display it. The program is based on Windows Python. Here are the features: Only FFMPEG is used (no ffprobe), first for getting the video dimension and then for video decoding. The FFMPEG is shutdown down gracefully if possible.

import numpy as np import cv2 import subprocess as sp import threading import sys import re import time class VidDecCtx(): FFMPEG_CMD = [ \ 'c:\\Program Files (x86)\\WinFF\\ffmpeg.exe', '-i', 'pipe:', \ '-f', 'rawvideo', '-pix_fmt', 'bgr24', '-an', '-sn', 'pipe:' \ ] DEFAULT_STOP_CNT = 100 READ_BUF_SIZE = 1024 READ_DECODE_BUF_SIZE = 100*1024 def __init__(self): self.process = None self.pthread = None self.buf = bytearray() self.fp = None self.toStopRunCnt = 0 self.isRunning = False def openVidFile(self, vFile): try: self.fp = open(vFile, 'rb') except Exception as e: self.fp = None return False return True def writer(self, toBuffer): while self.isRunning: if not toBuffer and len(self.buf)>0: time.sleep(0) byte_s = self.buf[0:VidDecCtx.READ_BUF_SIZE] self.buf = self.buf[VidDecCtx.READ_BUF_SIZE:] else: byte_s = self.fp.read(VidDecCtx.READ_BUF_SIZE) if toBuffer: self.buf += bytearray(byte_s) if not byte_s: break self.process.stdin.write(byte_s) self.toStopRunCnt = (self.toStopRunCnt-1) if self.toStopRunCnt>0 else 0 if self.toStopRunCnt==1: break self.process.stdin.close() self.toStopRunCnt = 0 self.isRunning = False def prepareGetDim(self): self.process = sp.Popen(VidDecCtx.FFMPEG_CMD, stdin=sp.PIPE, stderr=sp.STDOUT, \ stdout=sp.PIPE, bufsize=VidDecCtx.READ_DECODE_BUF_SIZE) self.isRunning = True self.pthread = threading.Thread(target=self.writer, args=[True]) self.pthread.start() def prepareDecode(self): self.process = sp.Popen(VidDecCtx.FFMPEG_CMD, stdin=sp.PIPE, stderr=sp.DEVNULL, \ stdout=sp.PIPE, bufsize=VidDecCtx.READ_BUF_SIZE) self.isRunning = True self.pthread = threading.Thread(target=self.writer, args=[False]) self.pthread.start() def stopThread(self): # need to continue to feed some data so that can quit gracefully self.toStopRunCnt = VidDecCtx.DEFAULT_STOP_CNT def cleanupThread(self): if self.pthread is not None: self.pthread.join() self.pthread=None if self.process is not None: try: self.process.wait(0.1) except (sp.TimeoutExpired): self.process.kill() self.process = None def finish(self): if self.fp is not None: self.fp.close() self.fp = None class LineBuffer(): def __init__(self): self.strBuf = bytearray() self.prevStrBufSearchIdx = 0 def feedBytes(self, byte_s): # Extract printable characters, and process line bye line tmp = filter(lambda x: x==0xa or x==0xd or (x>=0x20 and x<=0x7f), byte_s) self.strBuf += bytearray(tmp) def getLine(self): tmp=self.strBuf.find(0xa, self.prevStrBufSearchIdx) if tmp==-1: self.prevStrBufSearchIdx = len(self.strBuf) return None else: # do something to self.strBuf[:tmp] tmpStr=self.strBuf[:tmp].decode() self.strBuf = self.strBuf[tmp+1:] self.prevStrBufSearchIdx=0 return tmpStr if __name__ == "__main__": if len(sys.argv)!=2: print("Usage: c:\Python\python37\python %s vFile"%sys.argv[0], file=sys.stderr) sys.exit() vDCtx = VidDecCtx() lineBuf = LineBuffer() if not vDCtx.openVidFile(sys.argv[1]): print("Failed to open %s"%sys.argv[1], file=sys.stderr) sys.exit() width = None height = None bufSize = 1024 dimRegEx = re.compile(' *?Stream #.*?Video:.*?, *(\d+)x(\d+),') ######################################### # get dimension vDCtx.prepareGetDim() while vDCtx.isRunning: in_bytes = vDCtx.process.stdout.read(bufSize) if not in_bytes: break; if width is None: lineBuf.feedBytes(in_bytes) while True: tmpStr=lineBuf.getLine() if tmpStr is None: break tmpMatch=dimRegEx.match(tmpStr) if tmpMatch is not None: width=int(tmpMatch.group(1)) height=int(tmpMatch.group(2)) vDCtx.stopThread() break vDCtx.cleanupThread() if width is None: print("Failed to get the dimension of video", file=sys.stderr) sys.exit() print("Video dimension: (%d,%d)"%(width, height), file=sys.stderr) print("Buffered video data: %d"%(len(vDCtx.buf)), file=sys.stderr) ######################################### # decoding bufSize=width*height*3 vDCtx.prepareDecode() while vDCtx.isRunning: in_bytes = vDCtx.process.stdout.read(bufSize) if not in_bytes: break; # Transform the byte read into a NumPy array in_frame = (np.frombuffer(in_bytes, np.uint8).reshape([height, width, 3])) # Display the frame (for testing) cv2.imshow('in_frame', in_frame) if cv2.waitKey(1) & 0xFF == ord('q'): vDCtx.stopThread() vDCtx.cleanupThread() vDCtx.finish()