庆祝期末考试结束的最好办法就是不歇气写10个小时的代码。
从pass的办法衍生出来，其实也不完全一样，只是思路有点像。
证明：

aaa:乐视云
aab:本地
都用ffmpeg直接解流不再封装，直接比对hash
# md5sum aaa.aac      aab.aac
ac9fb614c863349835f51d41b390d400  aaa.aac
ac9fb614c863349835f51d41b390d400  aab.aac
# md5sum aaa.h264     aab.h264
1670d9a42f32d8746994bd54129ba3d7  aaa.h264
1670d9a42f32d8746994bd54129ba3d7  aab.h264

代码：
https://github.com/cnbeining/audioblacker
再来一份扔下面。

#!/usr/bin/env python
#coding:utf-8
# Author:  Beining --<ACICFG>
# Contact: http://www.cnbeining.com/   |https://github.com/cnbeining/audioblacker
# Purpose: Patch video's audio part to bypass Letvcloud's transcode.
# Created: 08/21/2014
# LICENSE: GNU v2
import sys
import os
import os, sys, subprocess, shlex, re
from subprocess import call
import uuid
import math
import shutil
import getopt
#----------------------------------------------------------------------
def probe_file(filename):
    cmnd = ['ffprobe', '-show_format', '-pretty', '-loglevel', 'quiet', filename]
    p = subprocess.Popen(cmnd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    #print filename
    out, err =  p.communicate()
    #print out
    if err:
        print err
        return None
    return out
#----------------------------------------------------------------------
def time_to_sec(time_raw):
    """
    str->int
    ignore .*."""
    hr = int(time_raw.split(':')[0]) * 3600
    minute = int(time_raw.split(':')[1]) * 60
    sec = int(float(time_raw.split(':')[2]))
    return int(hr + minute + sec)
#----------------------------------------------------------------------
def get_abspath(filename):
    """"""
    return str(os.path.abspath(filename))
#----------------------------------------------------------------------
def process(filename, target_bitrate, audiobitrate, safe, outputfile):
    """str,int,int,str->?
    filename,outputfile comes with the path.
    safe=0: directly convert the file to m4a"""
    tmpdir = '/tmp/Audioblacker-' + str(uuid.uuid4())
    if not os.path.exists(tmpdir):
        os.makedirs(tmpdir)
    audio_format = ''
    audio_duration = ''
    audio_bitrate = ''
    video_format = ''
    video_duration = ''
    video_bitrate = ''
    #demux audio file
    # Add this to save time, for experienced users
    print('INFO: Checking audio and remux...')
    if safe == 0:
        #directly to m4a to save space
        os.system('ffmpeg -i \'' + filename + '\' -vn -c:a copy ' + tmpdir+'/audio.m4a' +'> /dev/null 2>&1')
        try:
            for line in probe_file(tmpdir+'/audio.m4a').split('\n'):
                #print(line)
                if 'duration' in line:
                    audio_duration = str(line.split('=')[1])
        except:
            print('ERROR: Cannot read audio file!')
            exit()
    else:
        os.system('ffmpeg -i \'' + filename + '\' -vn -c:a copy ' + tmpdir+'/audio.aac' +'> /dev/null 2>&1')
        try:
            for line in probe_file(tmpdir+'/audio.aac').split('\n'):
                    if 'format_name' in line:
                        audio_format = str(line.split('=')[1])
                    if 'duration' in line:
                        audio_duration = str(line.split('=')[1])
            print('INFO: Audio safe, converting to m4a and clean cache...')
            os.system('ffmpeg -i '+ tmpdir+'/audio.aac -vn -c:a copy ' + tmpdir+'/audio.m4a' +'> /dev/null 2>&1')
            try:
                os.remove(tmpdir+'/audio.aac')
            except:
                print('WARNING: Cannot remove the aac file now...')
        except:
            print('ERROR: Cannot read audio file!')
            exit()
        #In case someone screw the audio up
        if not 'aac' in audio_format:
            print('ERROR: You have to use AAC as audio format!')
            exit()
    #Check original file
    try:
        for line in probe_file(filename).split('\n'):
                if 'duration' in line:
                    video_duration = str(line.split('=')[1])
    except:
        print('ERROR: Cannot read video file!')
        exit()
    #Calc...
    #time_by_video
    print('INFO: Doing calculation...')
    video_duration_sec = time_to_sec(video_duration)
    video_size_byte = int(os.path.getsize(filename))
    audio_duration_sec = time_to_sec(audio_duration)
    audio_size_byte = int(os.path.getsize(tmpdir+'/audio.m4a'))
    #!!!!!FLOAT DUE TO ACCURACY!!!!!
    target_byterate = target_bitrate / 8
    target_audiobyterate = audiobitrate / 8
    time_video = int(math.ceil((video_size_byte - target_byterate * video_duration_sec) / (target_byterate - 300)))
    time_audio = int(math.ceil((audio_size_byte - target_audiobyterate * audio_duration_sec) / (target_audiobyterate - 300)))
    if time_audio < 0 and time_video < 0:
        print('ERROR: Cannot calculate target, your target bitrate is higher than the original file!')
        shutil.rmtree(tmpdir)
        exit()
    if time_audio == 0 and time_video == 0:
        time_patch = 60
    elif time_audio > time_video:
        time_patch = time_audio + 10
    else:
        time_patch = time_video + 10
    #Make audio patch
    f = open(tmpdir + '/audiocode.txt', 'w')
    ff = 'file \'' + tmpdir + '/audio.m4a\'' + '\n'
    os.getcwd()
    py_path = sys.path[0]
    os.chdir(py_path)
    for i in range(time_patch):
        ff = ff + 'file \'' + str(os.getcwd()) + '/'+ '1sblack.m4a\'' + '\n'
    ff = ff.encode("utf8")
    f.write(ff)
    f.close()
    print('INFO: Concating audios...')
    os.system('ffmpeg -f concat -i '+ tmpdir + '/audiocode.txt -c copy '+ tmpdir +'/audiopatched.m4a'+'> /dev/null 2>&1')
    print('INFO: Making final output file...')
    os.system('ffmpeg -i ' + filename + ' -i ' + tmpdir +'/audiopatched.m4a -c copy  -map 0:0 -map 1:0 '+outputfile +'> /dev/null 2>&1')
    print('Done!')
    #clean up
    try:
        shutil.rmtree(tmpdir)
    except:
        print('ERROR: Cannot remove temp dir, do it by yourself!')
#----------------------------------------------------------------------
def usage():
    """"""
    print('''Usage:
    python audioblacker.py (-h) (-i input.mp4) (-o output.mp4) (-b 1990000) (-a 120000) (-s 1)
    -h: Default: None
        Help.
    -i: Default: Blank
        Input file.
        If the file and audioblacker are not under the same path,
        it is suggested to use absolute path to avoid possible failure.
    -o Default: input-filename.black.mp4
       Output file.
       Would be in the same folder with the original file if not specified.
    -b: Default: 1990000
        Target bitrate.
    -a: Default: 110000
        Target audio bitrate.
    audioblacker would calculate both of the required black time,
    and choose the larger one to make sure your convert is successful.
    -s: Default: 1
        Use safe mode.
        audioblacker would check whether the file's audio is AAC.
        Disabling would save you some space and time,
        if you know what you are doing.
        ''')
#----------------------------------------------------------------------
if __name__=='__main__':
    argv_list = []
    argv_list = sys.argv[1:]
    filename = ''
    target_bitrate = 1990000
    outputfile = ''
    safe = 1
    audiobitrate = 110000
    try:
        opts, args = getopt.getopt(argv_list, "hi:b:a:o:s:", ['help', 'input','bitrate', 'audiobitrate'
                                                           'outputfile', 'safe'])
    except getopt.GetoptError:
        usage()
        exit()
    for o, a in opts:
        if o in ('-h', '--help'):
            usage()
            exit()
        elif o in ('-i', '--input'):
            filename = a
            try:
                argv_list.remove('-i')
            except:
                break
        elif o in ('-b', '--bitrate'):
            target_bitrate = int(a)
            try:
                argv_list.remove('-b')
            except:
                break
        elif o in ('-a', '--audiobitrate'):
            audiobitrate = int(a)
            try:
                argv_list.remove('-a')
            except:
                break
        elif o in ('-o', '--outputfile'):
            outputfile = a
            try:
                argv_list.remove('-o')
            except:
                break
        elif o in ('-s', '--safe'):
            safe = int(a)
            try:
                argv_list.remove('-s')
            except:
                break
    if filename == '':
        print('ERROR: No input file!')
        exit()
    if outputfile == '':
        outputfile = filename.split('.')[0] + '.black.mp4'
    process(filename, target_bitrate, audiobitrate, safe, outputfile)