The VideoLAN Forums

Posted: **04 Oct 2011 00:58**

Hello,

I try to convert an flv file to another container (for example avi).

The file I'm trying to convert can be downloaded until 24th october 2011 here:
http://www.megaupload.com/?d=7ZY9WUB8

I had no luck so far with ffmpeg, mencoder, flvextract and mkvmerge. So I tried vlc version 1.1.9 but also without luck. The file should be 27:40 min and at 11:31 min the woman speaks.

Does someone have an idea how to convert that file with correct a/v synchronization ?

Thanks

Posted: **04 Oct 2011 09:45**

The timestamps of this file are badly broken, maybe because of the low FPS used and/or the variable framerate and/or a bad source and/or a poor file writing app, and I'm not sure what to do since the playback is already jerky. Try with AviDemux or maybe some DirectShow through GraphEdit solution.

Code: Select all

General
Format                           : Flash Video
_videodevice                     : USB-Videogert
_framerate                       : 20.000

Video
Format                           : AVC
Frame rate mode                  : Variable
Frame rate                       : 10.000 fps

Posted: **04 Oct 2011 16:36**

Hello Lotesdelere,

thank you for looking at the file.

I recorded the FLV file from a video stream of dacast.com with rtmpsuck version 2.3.

svn://svn.mplayerhq.hu/rtmpdump
revision: 569

Not sure whether rtmpsuck is the problem, dacast.com or whatever.

The timestamps of this file are badly broken

Currently, I try to understand what the timecodes of FLVExtract can tell me.

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wget http://moitah.net/download/latest/FLV_Extract.zip
unzip FLV_Extract.zip
mono FLVExtractCL.exe -v -a -t videostream_2011-09-27_23-42-16.flv

The command above produces 3 files:
1. video: 27:56 min, H.264
2. audio: 27:40 min, MP3
3. timecodes: 16768 lines at 10 frames per second = 1676.7 seconds = 27:56 min

When I look at the timecodes, I can see 125 times 0 at the beginning:

Code: Select all

less -N videostream_2011-09-27_23-42-16.txt

At 10 frames per second, each line seems to represent 0.1 seconds.

As far as I understand, this means that with 125 lines 0 I have to skip 12.5 seconds of the video to be in sync with the audio

?

What I do not understand are the mixed values of relative and absolute times in the timecodes:

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line 127: 63
line 128: 163
line 129: 14051989
...
line 202: 14059289
line 203: 7663
line 204: 14059489

Line 127 contains the relative value 0.063 seconds since the start of the video and line 203 is 7.663 seconds since the start of the video.
Besides that are absolute values like 14051989 == 14051.989 seconds == 3:54:12 which could be the start of the video stream from the webserver

?

What I am going to try is cut the video at the beginning by 12.5 seconds and at the end so that audio and video have the same length. After that audio and video could be multiplexed together.

If I have success, I'm going to post the program / command lines that I use.

Posted: **05 Oct 2011 09:50**

I recorded the FLV file from a video stream of dacast.com with rtmpsuck version 2.3.

You should use RtmpDump itself which is, as its name says, the dedicated tool for dumping a stream.

I don't know much about FLVExtract because I'm usually using FFmpeg like this:

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ffmpeg -i videostream.flv -vcodec copy -acodec copy output.mp4

Anyway, this is the VLC forum. If you want more information about FLVExtract, timecodes and the FLV format itself I suggest you to go to dedicated forums such as Doom9.org, Doom10.org and VideoHelp.com.

Posted: **08 Oct 2011 18:47**

Meanwhile I a found a conversion that works more or less. So I post my bash script just in case someone else has the same problem:

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#!/bin/bash

if [ ! $# -eq 1 ];then
 echo "Use the flv file as parameter"
 exit 1
fi

# remove existing video streams from RAM disk
rm -f /dev/shm/video*

# extract audio, video and timecodes
mono FLVExtractCL.exe -d /dev/shm/ -v -a -t "$1"

# create index for flv video
ffmpeg -y -i /dev/shm/*.264 -vcodec copy /dev/shm/video.mp4

# remove the h264 video to get more free space
rm -f /dev/shm/*.264

# calculate an offset for audio and video synchronization
offset=$(expr $(grep "^0$" /dev/shm/videostream*.txt | wc -l) - 1 | sed 's/\(.*\)\(.\)$/\1.\2/')

# multiplex audio and video together with mencoder with an offset
mencoder /dev/shm/video.mp4 -audiofile /dev/shm/video*.mp3 -oac copy -ovc copy -delay -$offset -o /dev/shm/video.avi

Anyway, this is the VLC forum. If you want more information about FLVExtract, timecodes and the FLV format itself I suggest you to go to dedicated forums such as Doom9.org, Doom10.org and VideoHelp.com.

OK. I see that VLC is currently not able to play or convert that particular FLV file. I'll have a try at Doom9.org.

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