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26 septembre 2011, par
Mis à jour : Avril 2013
Langue : English
Type : Audio
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-
ffmpeg takes a while to start
17 octobre 2020, par SuspendedI have this command in python script, in a loop :


ffmpeg -i somefile.mp4 -ss 00:03:12 -t 00:00:35 piece.mp4 -loglevel error -stats


It cuts out pieces of input file (-i). Input filename, as well as start time (-ss) and length of the piece I cut out (-t) varies, so it reads number of mp4 files and cuts out number of pieces from each one. During execution of the script it might be called around 100 times. My problem is that each time before it starts, there is a delay of few seconds and it adds up to significant time. How can I get it to start immediately ?


The script (process_videos.py) :


import subprocess
import sys
import math
import time

class TF:
 """TimeFormatter class (TF).
This class' reason for being is to convert time in short
form, e.g. 1:33, 0:32, or 23 into long form accepted by
mp4cut function in bash, e.g. 00:01:22, 00:00:32, etc"""

def toLong(self, shrt):
 """Converts time to its long form"""
 sx = '00:00:00'
 ladd = 8 - len(shrt)
 n = sx[:ladd] + shrt
 return n

def toShort(self, lng):
 """Converts time to short form"""
 if lng[0] == '0' or lng[0] == ':':
 return self.toShort(lng[1:])
 else:
 return lng

def toSeconds(self, any_time):
 """Converts time to seconds"""
 if len(any_time) < 3:
 return int(any_time)
 tt = any_time.split(':')
 if len(any_time) < 6: 
 return int(tt[0])*60 + int(tt[1])
 return int(tt[0])*3600 + int(tt[1])*60 + int(tt[2])

def toTime(self, secsInt):
 """"""
 tStr = ''
 hrs, mins, secs = 0, 0, 0
 if secsInt >= 3600:
 hrs = math.floor(secsInt / 3600)
 secsInt = secsInt % 3600
 if secsInt >= 60:
 mins = math.floor(secsInt / 60)
 secsInt = secsInt % 60
 secs = secsInt
 return str(hrs).zfill(2) + ':' + str(mins).zfill(2) + ':' + str(secs).zfill(2)

def minus(self, t_start, t_end):
 """"""
 t_e = self.toSeconds(t_end)
 t_s = self.toSeconds(t_start)
 t_r = t_e - t_s
 hrs, mins, secs = 0, 0, 0
 if t_r >= 3600:
 hrs = math.floor(t_r / 3600)
 t_r = t_r - (hrs * 3600)
 if t_r >= 60:
 mins = math.floor(t_r / 60)
 t_r = t_r - (mins * 60)
 secs = t_r
 hrsf = str(hrs).zfill(2)
 minsf = str(mins).zfill(2)
 secsf = str(secs).zfill(2)
 t_fnl = hrsf + ':' + minsf + ':' + secsf
 return t_fnl

def go_main():
 tf = TF()
 vid_n = 0
 arglen = len(sys.argv)
 if arglen == 2:
 with open(sys.argv[1], 'r') as f_in:
 lines = f_in.readlines()
 start = None
 end = None
 cnt = 0
 for line in lines:
 if line[:5] == 'BEGIN':
 start = cnt
 if line[:3] == 'END':
 end = cnt
 cnt += 1
 if start == None or end == None:
 print('Invalid file format. start = {}, end = {}'.format(start,end))
 return
 else:
 lines_r = lines[start+1:end]
 del lines
 print('videos to process: {}'.format(len(lines_r)))
 f_out_prefix = ""
 for vid in lines_r:
 vid_n += 1
 print('\nProcessing video {}/{}'.format(vid_n, len(lines_r)))
 f_out_prefix = 'v' + str(vid_n) + '-'
 dat = vid.split('!')[1:3]
 title = dat[0]
 dat_t = dat[1].split(',')
 v_pieces = len(dat_t)
 piece_n = 0
 video_pieces = []
 cmd1 = "echo -n \"\" > tmpfile"
 subprocess.run(cmd1, shell=True) 
 print(' new tmpfile created')
 for v_times in dat_t:
 piece_n += 1
 f_out = f_out_prefix + str(piece_n) + '.mp4'
 video_pieces.append(f_out)
 print(' piece filename {} added to video_pieces list'.format(f_out))
 v_times_spl = v_times.split('-')
 v_times_start = v_times_spl[0]
 v_times_end = v_times_spl[1]
 t_st = tf.toLong(v_times_start)
 t_dur = tf.toTime(tf.toSeconds(v_times_end) - tf.toSeconds(v_times_start))
 cmd3 = ["ffmpeg", "-i", title, "-ss", t_st, "-t", t_dur, f_out, "-loglevel", "error", "-stats"]
 print(' cutting out piece {}/{} - {}'.format(piece_n, len(dat_t), t_dur))
 subprocess.run(cmd3)
 for video_piece_name in video_pieces:
 cmd4 = "echo \"file " + video_piece_name + "\" >> tmpfile"
 subprocess.run(cmd4, shell=True)
 print(' filename {} added to tmpfile'.format(video_piece_name))
 vname = f_out_prefix[:-1] + ".mp4"
 print(' name of joined file: {}'.format(vname))
 cmd5 = "ffmpeg -f concat -safe 0 -i tmpfile -c copy joined.mp4 -loglevel error -stats"
 to_be_joined = " ".join(video_pieces)
 print(' joining...')
 join_cmd = subprocess.Popen(cmd5, shell=True)
 join_cmd.wait()
 print(' joined!')
 cmd6 = "mv joined.mp4 " + vname
 rename_cmd = subprocess.Popen(cmd6, shell=True)
 rename_cmd.wait()
 print(' File joined.mp4 renamed to {}'.format(vname))
 cmd7 = "rm " + to_be_joined
 rm_cmd = subprocess.Popen(cmd7, shell=True)
 rm_cmd.wait()
 print('rm command completed - pieces removed')
 cmd8 = "rm tmpfile"
 subprocess.run(cmd8, shell=True)
 print('tmpfile removed')
 print('All done')
 else:
 print('Incorrect number of arguments')

############################
if __name__ == '__main__':
 go_main()


process_videos.py is called from bash terminal like this :


$ python process_videos.py video_data 


video_data file has the following format :


BEGIN
!first_video.mp4!3-23,55-1:34,2:01-3:15,3:34-3:44!
!second_video.mp4!2-7,12-44,1:03-1:33!
END


My system details :


System: Host: snowflake Kernel: 5.4.0-52-generic x86_64 bits: 64 Desktop: Gnome 3.28.4
 Distro: Ubuntu 18.04.5 LTS
Machine: Device: desktop System: Gigabyte product: N/A serial: N/A
Mobo: Gigabyte model: Z77-D3H v: x.x serial: N/A BIOS: American Megatrends v: F14 date: 05/31/2012
CPU: Quad core Intel Core i5-3570 (-MCP-) cache: 6144 KB 
 clock speeds: max: 3800 MHz 1: 1601 MHz 2: 1601 MHz 3: 1601 MHz 4: 1602 MHz
Drives: HDD Total Size: 1060.2GB (55.2% used)
 ID-1: /dev/sda model: ST31000524AS size: 1000.2GB
 ID-2: /dev/sdb model: Corsair_Force_GT size: 60.0GB
Partition: ID-1: / size: 366G used: 282G (82%) fs: ext4 dev: /dev/sda1
 ID-2: swap-1 size: 0.70GB used: 0.00GB (0%) fs: swap dev: /dev/sda5
Info: Processes: 313 Uptime: 16:37 Memory: 3421.4/15906.9MB Client: Shell (bash) inxi: 2.3.56


-
ffmpeg takes too long to start
17 octobre 2020, par SuspendedI have this command in python script, in a loop :


ffmpeg -i somefile.mp4 -ss 00:03:12 -t 00:00:35 piece.mp4 -loglevel error -stats


It cuts out pieces of input file (-i). Input filename, as well as start time (-ss) and length of the piece I cut out (-t) varies, so it reads number of mp4 files and cuts out number of pieces from each one. During execution of the script it might be called around 100 times. My problem is that each time before it starts, there is a delay of 6-15 seconds and it adds up to significant time. How can I get it to start immediately ?


Initially I thought it was process priority problem, but I noticed that even during the "pause", all processors work at 100%, so apparently some work is being done.


The script (process_videos.py) :


import subprocess
import sys
import math
import time

class TF:
 """TimeFormatter class (TF).
This class' reason for being is to convert time in short
form, e.g. 1:33, 0:32, or 23 into long form accepted by
mp4cut function in bash, e.g. 00:01:22, 00:00:32, etc"""

def toLong(self, shrt):
 """Converts time to its long form"""
 sx = '00:00:00'
 ladd = 8 - len(shrt)
 n = sx[:ladd] + shrt
 return n

def toShort(self, lng):
 """Converts time to short form"""
 if lng[0] == '0' or lng[0] == ':':
 return self.toShort(lng[1:])
 else:
 return lng

def toSeconds(self, any_time):
 """Converts time to seconds"""
 if len(any_time) < 3:
 return int(any_time)
 tt = any_time.split(':')
 if len(any_time) < 6: 
 return int(tt[0])*60 + int(tt[1])
 return int(tt[0])*3600 + int(tt[1])*60 + int(tt[2])

def toTime(self, secsInt):
 """"""
 tStr = ''
 hrs, mins, secs = 0, 0, 0
 if secsInt >= 3600:
 hrs = math.floor(secsInt / 3600)
 secsInt = secsInt % 3600
 if secsInt >= 60:
 mins = math.floor(secsInt / 60)
 secsInt = secsInt % 60
 secs = secsInt
 return str(hrs).zfill(2) + ':' + str(mins).zfill(2) + ':' + str(secs).zfill(2)

def minus(self, t_start, t_end):
 """"""
 t_e = self.toSeconds(t_end)
 t_s = self.toSeconds(t_start)
 t_r = t_e - t_s
 hrs, mins, secs = 0, 0, 0
 if t_r >= 3600:
 hrs = math.floor(t_r / 3600)
 t_r = t_r - (hrs * 3600)
 if t_r >= 60:
 mins = math.floor(t_r / 60)
 t_r = t_r - (mins * 60)
 secs = t_r
 hrsf = str(hrs).zfill(2)
 minsf = str(mins).zfill(2)
 secsf = str(secs).zfill(2)
 t_fnl = hrsf + ':' + minsf + ':' + secsf
 return t_fnl

def go_main():
 tf = TF()
 vid_n = 0
 arglen = len(sys.argv)
 if arglen == 2:
 with open(sys.argv[1], 'r') as f_in:
 lines = f_in.readlines()
 start = None
 end = None
 cnt = 0
 for line in lines:
 if line[:5] == 'BEGIN':
 start = cnt
 if line[:3] == 'END':
 end = cnt
 cnt += 1
 if start == None or end == None:
 print('Invalid file format. start = {}, end = {}'.format(start,end))
 return
 else:
 lines_r = lines[start+1:end]
 del lines
 print('videos to process: {}'.format(len(lines_r)))
 f_out_prefix = ""
 for vid in lines_r:
 vid_n += 1
 print('\nProcessing video {}/{}'.format(vid_n, len(lines_r)))
 f_out_prefix = 'v' + str(vid_n) + '-'
 dat = vid.split('!')[1:3]
 title = dat[0]
 dat_t = dat[1].split(',')
 v_pieces = len(dat_t)
 piece_n = 0
 video_pieces = []
 cmd1 = "echo -n \"\" > tmpfile"
 subprocess.run(cmd1, shell=True) 
 print(' new tmpfile created')
 for v_times in dat_t:
 piece_n += 1
 f_out = f_out_prefix + str(piece_n) + '.mp4'
 video_pieces.append(f_out)
 print(' piece filename {} added to video_pieces list'.format(f_out))
 v_times_spl = v_times.split('-')
 v_times_start = v_times_spl[0]
 v_times_end = v_times_spl[1]
 t_st = tf.toLong(v_times_start)
 t_dur = tf.toTime(tf.toSeconds(v_times_end) - tf.toSeconds(v_times_start))
 cmd3 = ["ffmpeg", "-i", title, "-ss", t_st, "-t", t_dur, f_out, "-loglevel", "error", "-stats"]
 print(' cutting out piece {}/{} - {}'.format(piece_n, len(dat_t), t_dur))
 subprocess.run(cmd3)
 for video_piece_name in video_pieces:
 cmd4 = "echo \"file " + video_piece_name + "\" >> tmpfile"
 subprocess.run(cmd4, shell=True)
 print(' filename {} added to tmpfile'.format(video_piece_name))
 vname = f_out_prefix[:-1] + ".mp4"
 print(' name of joined file: {}'.format(vname))
 cmd5 = "ffmpeg -f concat -safe 0 -i tmpfile -c copy joined.mp4 -loglevel error -stats"
 to_be_joined = " ".join(video_pieces)
 print(' joining...')
 join_cmd = subprocess.Popen(cmd5, shell=True)
 join_cmd.wait()
 print(' joined!')
 cmd6 = "mv joined.mp4 " + vname
 rename_cmd = subprocess.Popen(cmd6, shell=True)
 rename_cmd.wait()
 print(' File joined.mp4 renamed to {}'.format(vname))
 cmd7 = "rm " + to_be_joined
 rm_cmd = subprocess.Popen(cmd7, shell=True)
 rm_cmd.wait()
 print('rm command completed - pieces removed')
 cmd8 = "rm tmpfile"
 subprocess.run(cmd8, shell=True)
 print('tmpfile removed')
 print('All done')
 else:
 print('Incorrect number of arguments')

############################
if __name__ == '__main__':
 go_main()


process_videos.py is called from bash terminal like this :


$ python process_videos.py video_data 


video_data file has the following format :


BEGIN
!first_video.mp4!3-23,55-1:34,2:01-3:15,3:34-3:44!
!second_video.mp4!2-7,12-44,1:03-1:33!
END


My system details :


System: Host: snowflake Kernel: 5.4.0-52-generic x86_64 bits: 64 Desktop: Gnome 3.28.4
 Distro: Ubuntu 18.04.5 LTS
Machine: Device: desktop System: Gigabyte product: N/A serial: N/A
Mobo: Gigabyte model: Z77-D3H v: x.x serial: N/A BIOS: American Megatrends v: F14 date: 05/31/2012
CPU: Quad core Intel Core i5-3570 (-MCP-) cache: 6144 KB 
 clock speeds: max: 3800 MHz 1: 1601 MHz 2: 1601 MHz 3: 1601 MHz 4: 1602 MHz
Drives: HDD Total Size: 1060.2GB (55.2% used)
 ID-1: /dev/sda model: ST31000524AS size: 1000.2GB
 ID-2: /dev/sdb model: Corsair_Force_GT size: 60.0GB
Partition: ID-1: / size: 366G used: 282G (82%) fs: ext4 dev: /dev/sda1
 ID-2: swap-1 size: 0.70GB used: 0.00GB (0%) fs: swap dev: /dev/sda5
Info: Processes: 313 Uptime: 16:37 Memory: 3421.4/15906.9MB Client: Shell (bash) inxi: 2.3.56



UPDATE :


Following Charles' advice, I used performance sampling :


# perf record -a -g sleep 180


...and here's the report :


Samples: 74K of event 'cycles', Event count (approx.): 1043554519767
 Children Self Command Shared Object
- 50.56% 45.86% ffmpeg libavcodec.so.57.107.100 
 - 3.10% 0x4489480000002825 
 0.64% 0x7ffaf24b92f0 
 - 2.12% 0x5f7369007265646f 
 av_default_item_name 
 1.39% 0 
- 44.48% 40.59% ffmpeg libx264.so.152 
 5.78% x264_add8x8_idct_avx2.skip_prologue 
 3.13% x264_add8x8_idct_avx2.skip_prologue 
 2.91% x264_add8x8_idct_avx2.skip_prologue 
 2.31% x264_add8x8_idct_avx.skip_prologue 
 2.03% 0 
 1.78% 0x1 
 1.26% x264_add8x8_idct_avx2.skip_prologue 
 1.09% x264_add8x8_idct_avx.skip_prologue 
 1.06% x264_me_search_ref 
 0.97% x264_add8x8_idct_avx.skip_prologue 
 0.60% x264_me_search_ref 
- 38.01% 0.00% ffmpeg [unknown] 
 4.10% 0 
 - 3.49% 0x4489480000002825 
 0.70% 0x7ffaf24b92f0 
 0.56% 0x7f273ae822f0 
 0.50% 0x7f0c4768b2f0 
 - 2.29% 0x5f7369007265646f 
 av_default_item_name 
 1.99% 0x1 
 10.13% 10.12% ffmpeg [kernel.kallsyms] 
- 3.14% 0.73% ffmpeg libavutil.so.55.78.100 
 2.34% av_default_item_name 
- 1.73% 0.21% ffmpeg libpthread-2.27.so 
 - 0.70% pthread_cond_wait@@GLIBC_2.3.2 
 - 0.62% entry_SYSCALL_64_after_hwframe 
 - 0.62% do_syscall_64 
 - 0.57% __x64_sys_futex 
 0.52% do_futex 
 0.93% 0.89% ffmpeg libc-2.27.so 
- 0.64% 0.64% swapper [kernel.kallsyms] 
 0.63% secondary_startup_64 
 0.21% 0.18% ffmpeg libavfilter.so.6.107.100 
 0.20% 0.11% ffmpeg libavformat.so.57.83.100 
 0.12% 0.11% ffmpeg ffmpeg 
 0.11% 0.00% gnome-terminal- [unknown] 
 0.09% 0.07% ffmpeg libm-2.27.so 
 0.08% 0.07% ffmpeg ld-2.27.so 
 0.04% 0.04% gnome-terminal- libglib-2.0.so.0.5600.4




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