如何获取MP3文件（VBR或CBR）服务器端的实际持续时间 [英] How to get the real, actual duration of an MP3 file (VBR or CBR) server-side

问题描述

我曾经用ffmpeg来计算MP3文件服务器端的持续时间，这似乎工作正常。今天我发现一些计算是错误的。不知何故，由于某种原因，ffmpeg将会错误计算持续时间，并且似乎只发生可变比特率mp3文件。

在本地测试时，我注意到ffmpeg打印了两个

使用的命令：

  ffmpeg -i song_9747c077aef8.mp3 
  

ffmpeg说：

  [mp3 @ 0x102052600] max_analyze_duration 5000000已达到5015510 
 [mp3 @ 0x102052600]从比特率估计持续时间，这可能不准确
  pre> 
 
 
在一个不错的，热门的Google会话后，我发现了一些帖子，但没有找到解决方案。
 
 
 
然后我尝试增加最长时间：
  ffmpeg -analyzeduration 999999999 -i song_9747c077aef8.mp3 
  
此后，ffmpeg只返回第二行：
  [mp3 @ 0x102052600]从比特率估计持续时间，这可能是我naccurate 
  
但是无论在哪种情况下，计算的持续时间都是错误的。比较VLC我注意到持续时间是正确的。
 
 
 
经过更多的研究，我偶然发现了我安装和使用的mp3info。
  mp3info -p％Ssong_9747c077aef8.mp3 
  
 mp3info，然后返回 CORRECT 持续时间，但只能作为一个整数，我不能使用，因为我需要一个更准确的数字。原因是在下面的评论中解释，用户 blahdiblah   -  mp3info只是从文件中拉出ID3信息，实际上不执行任何计算。
 
 
 
我还尝试使用mplayer来检索持续时间，但是像ffmpeg一样，mplayer返回错误的值。
解决方案
我终于找到了使用sox的这个问题的一个正确的解决方案 - 它返回正确的信息。
  sox file.mp3 -n stat 
样本阅读：19321344 
长度（秒）：219.062857 
缩放：2147483647.0 
最大幅度：1.000000 
最小幅度：-1.000000 
中线幅度： 0.000000 
平均值：0.141787 
平均幅度：0.000060 
 RMS幅度：0.191376 
最大增量：0.947598 
最小值delta：0.000000 
平均delta：0.086211 
 RMS delta：0.115971 
粗糙频率：4253 
音量调整：1.000 
  
 长度（秒）：219.062857  
 
I used to calculate the duration of MP3 files server-side using ffmpeg - which seemed to work fine. Today i discovered that some of the calculations were wrong. Somehow, for some reason, ffmpeg will miscalculate the duration and it seems to happen with variable bit rate mp3 files only.

When testing this locally, i noticed that ffmpeg printed two extra lines in green.

Command used:
ffmpeg -i song_9747c077aef8.mp3
ffmpeg says:
[mp3 @ 0x102052600] max_analyze_duration 5000000 reached at 5015510
[mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate
After a nice, warm google session, i discovered some posts on this, but no solution was found.

I then tried to increase the maximum duration:
ffmpeg -analyzeduration 999999999 -i song_9747c077aef8.mp3
After this, ffmpeg returned only the second line:
[mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate
But in either case, the calculated duration was just plain wrong. Comparing it to VLC i noticed that there the duration is correct.

After more research i stumbled over mp3info - which i installed and used.
mp3info -p "%S" song_9747c077aef8.mp3
mp3info then returned the CORRECT duration, but only as an integer, which i cannot use as i need a more accurate number here. The reason for this was explained in a comment below, by user blahdiblah - mp3info is simply pulling ID3 info from the file and not actually performing any calculations.

I also tried using mplayer to retrieve the duration, but just as ffmpeg, mplayer is returning the wrong value.
解决方案
I finally found a proper solution to this problem using sox - which returns the correct information.
sox file.mp3 -n stat
Samples read:          19321344
Length (seconds):    219.062857
Scaled by:         2147483647.0
Maximum amplitude:     1.000000
Minimum amplitude:    -1.000000
Midline amplitude:    -0.000000
Mean    norm:          0.141787
Mean    amplitude:     0.000060
RMS     amplitude:     0.191376
Maximum delta:         0.947598
Minimum delta:         0.000000
Mean    delta:         0.086211
RMS     delta:         0.115971
Rough   frequency:         4253
Volume adjustment:        1.000
Length (seconds):    219.062857

                        
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