Check keyframe alignment with ffprobe

gistfile1.py

#!/usr/bin/python
'''
This simple script allows you to input a file where you want to evaluate where the keyframes are
You simply input an infile that you want to evaluate
Where you expect the keyframes e.g. every 2 seconds
and the framerate e.g. 25 fps
It then scans the file and reports on where it expects keyframes and where they actually are

'''

import os
import re
import sys
import subprocess
import logging
import math

logger = logging.getLogger(__name__)

#infile = sys.argv[1]

#infile= "/tmp/ffmpeg_main_profile/out_gop12.ts"
infile = "/Users/andrew/Desktop/demo/vbvtests/bc_hls_1024x576.ts"
#target_dir = "/tmp/ffmpeg_main_profile/"

def get_keyframes(infile, keyframe_int, fps):
    # Should be able to return when keyframes are expected which is every x seconds
    # this would mean we should have an iframe every x * fps
    # Specific value for ffprobe output
    lines_past_type = 20
    line_count = 0
    print_line = False
    frame = 0
    found_iframe = False
    output_str = ""
    next_keyframe = math.ceil(float(fps) * keyframe_int)
    key_framedist = next_keyframe
    
    cmd = "ffprobe -show_frames %s" % infile
    
    logger.info(cmd)
# -print_format json
    process = subprocess.Popen(cmd,shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    
    while True:
      line = process.stdout.readline()
      if line != '':
        #the real code does filtering here
        #print line.rstrip()
        if (line.rstrip()=="media_type=video"):
            print_line = True
        if (print_line and (line_count < lines_past_type)):
            
                #print line.rstrip()
            if re.match(r'pict_type=I.*',line):
                found_iframe = True
                #print line.rstrip()
            match = re.match(r'coded_picture_number=(.*)',line)
            if (match):
                frame =  match.group(1)
                if (found_iframe):
                    output_str += "%s," % frame
                    found_iframe = False
                    if (int(frame)>=next_keyframe):
                        if (int(frame)==next_keyframe):
                            print "Found I frame as expected at %s" % next_keyframe
                        else:
                            print "Expected I frame at %s found at %s" % (next_keyframe, frame)
                        next_keyframe+=key_framedist
            
            line_count+=1
            if (line_count >= lines_past_type):
                print_line = False
                line_count = 0
      else:
        break
    return output_str

print get_keyframes(infile, 2, 25)

'''
[FRAME]
media_type=video
key_frame=1
pkt_pts=2499750
pkt_pts_time=27.775000
pkt_dts=2499750
pkt_dts_time=27.775000
pkt_duration=3750
pkt_duration_time=0.041667
pkt_pos=2905164
width=1280
height=720
pix_fmt=yuv420p
sample_aspect_ratio=1:1
pict_type=I
coded_picture_number=633
display_picture_number=0
interlaced_frame=0
top_field_first=0
repeat_pict=0
reference=3
[/FRAME]
'''