Posts Tagged ‘Set’

How to extract Audio Sound and Music from Flash Videos (.flv) files and convert it to (.mp3) on Linux and BSD

Friday, April 15th, 2011

In my quest to know Linux better and use it capabilities to fulfill a multimedia tasks I came across the question:

How can I extract audio sound and music from Flash Videos .flv file format?

After a bit of investigation online I’ve found out in order to achieve this task the quickest way is via the handy ffmpeg conversion tool .

It’s rather easy actually, all necessery to do the conversion is to have the ffmpeg installed.
FFMpeg is part of Debian and Ubuntu repositories, so if you haven’t installed it yet, go straigh and install it with:

debian:~# apt-get install ffmpeg
...

Many modern day Linux distributions already have the ffmpeg pre-installed by default, ffmpeg even have a Windows version so this little tutorial should be directly applied on a Windows host with installed ffmpeg.

Convertion of a .flv file to .mp3 file for example is a real piece of cake to so do issue the command:

debian:~# ffmpeg -i input_file.flv -ab 128 -ar 44100 output_file.mp3

The few mmpeg options meaning is as follows:

-i (specifies input file)
-ab (Set the audio bitrate in bit/s 64k by default)
-ar (Set the audio sampling frequency (default = 44100 Hz).)

For more options checkout the ffmpeg help.

I found ffmpeg to be a bit slower than I expected. A 17 minutes .flv video file is converted to .mp3 for 38 seconds time.

Here is the textual output I got on my Debian Linux while extracting the flash video’s sound and converting it to mp3:

debian:~# time ffmpeg -i g7tvI6JCXD0.flv -ab 128 -ar 44100 output.mp3
FFmpeg version SVN-r25838, Copyright (c) 2000-2010 the FFmpeg developers
built on Jan 21 2011 08:21:58 with gcc 4.4.5
configuration: –enable-libdc1394 –prefix=/usr –extra-cflags=’-Wall -g ‘ –cc=’ccache cc’ –enable-shared –enable-libmp3lame –enable-gpl –enable-libvorbis –enable-pthreads –enable-libfaac –enable-libxvid –enable-postproc –enable-x11grab –enable-libgsm –enable-libtheora –enable-libopencore-amrnb –enable-libopencore-amrwb –enable-libx264 –enable-libspeex –enable-nonfree –disable-stripping –enable-avfilter –enable-libdirac –disable-decoder=libdirac –enable-libschroedinger –disable-encoder=libschroedinger –enable-version3 –enable-libopenjpeg –enable-libvpx –enable-librtmp –extra-libs=-lgcrypt –disable-altivec –disable-armv5te –disable-armv6 –disable-vis
libavutil 50.33. 0 / 50.39. 0
libavcore 0.14. 0 / 0.14. 0
libavcodec 52.97. 2 / 52.97. 2
libavformat 52.87. 1 / 52.87. 1
libavdevice 52. 2. 2 / 52. 2. 2
libavfilter 1.65. 0 / 1.65. 0
libswscale 0.12. 0 / 0.12. 0
libpostproc 51. 2. 0 / 51. 2. 0
[flv @ 0x1336760] Estimating duration from bitrate, this may be inaccurate

Seems stream 0 codec frame rate differs from container frame rate: 2000.00 (2000/1) -> 29.92 (359/12)
Input #0, flv, from ‘g7tvI6JCXD0.flv’:
Metadata:
duration : 1060
starttime : 0
totalduration : 1060
width : 480
height : 360
videodatarate : 76
audiodatarate : 94
totaldatarate : 179
framerate : 30
bytelength : 23723246
canseekontime : true
sourcedata : B5F9E82C6HH1302704673918653
purl :
pmsg :
Duration: 00:17:40.35, start: 0.000000, bitrate: 174 kb/s
Stream #0.0: Video: h264, yuv420p, 480×360 [PAR 1:1 DAR 4:3], 77 kb/s, 29.92 tbr, 1k tbn, 2k tbc
Stream #0.1: Audio: aac, 44100 Hz, stereo, s16, 96 kb/s
WARNING: The bitrate parameter is set too low. It takes bits/s as argument, not kbits/s
Output #0, mp3, to ‘output.mp3’:
Metadata:
duration : 1060
starttime : 0
totalduration : 1060
width : 480
height : 360
videodatarate : 76
audiodatarate : 94
totaldatarate : 179
framerate : 30
bytelength : 23723246
canseekontime : true
sourcedata : B5F9E82C6HH1302704673918653
purl :
pmsg :
TSSE : Lavf52.87.1
Stream #0.0: Audio: libmp3lame, 44100 Hz, stereo, s16, 0 kb/s
Stream mapping:
Stream #0.1 -> #0.0
Press [q] to stop encoding
size= 16576kB time=1060.81 bitrate= 128.0kbits/s
video:0kB audio:16575kB global headers:0kB muxing overhead 0.002404%

real 0m38.489s
user 0m37.126s
sys 0m0.764s

When talking about conversions, another very useful application of ffmpeg is in case if you want to:

Extract Audio from online streams

Let’s say you have a favourite radio, you often listen and there are a podcast you want to capture for later listening, or just catch a few nice songs, using ffmpeg it’s a piece of cake by using the command like:

debian:~# ffmpeg -i http:///xxx.xxx.xxx.xxx/some -ab 128 -ar 44100 captured-radio-sound.mp3

The possible ways of use of ffmpeg is truly versatily, you can use it for instance if you have to convert some kind of audio or video format to another one I have given a very simple example of converting a .flv file to .avi and vice versa in my previous post

Speed up your DNS resolve if your Internet Service Provider DNS servers fail or resolve slowly / Privacy concerns of public DNS services use

Wednesday, March 30th, 2011

In my experience with many network Internet Service Providers by so far I’ve encountered a lot of DNS oddities and therefore surfing (web) and mail slowness.

It’s sometimes very irritating especially in cases, when I use my internet over Wireless public or university wireless networks.
In principle many of the Wireless routers which distribute the internet especially in organizations are badly configured and the slowness with DNS resolvings is an absolute classic.
If you haven’t encountered that slowness in opening web pages when connected from your University’s canteen, whether it’s fill with people for the lunch break, then I should say you’re really lucky!

My personal experience with this bad configured devices DNS services has been quite negative and every now and then I use to set and use public DNS servers like OpenDNS and Google DNS

Very often when I connect to a wireless network with my notebook running Debian Linux and the internet is too slow in opening pages I automatically set the Google or OpenDNS servers as a default DNS IP resolving servers.

1. DNS IP addresses of Google Public DNS are:

8.8.8.7
and
8.8.8.8

2. OpenDNS Public DNS servers has the IP addresses of:

208.67.222.222
208.67.222.220

I do set up and use the upper public DNS services addresses via the commands:

3. Set and use Google Public DNS services on my Linux debian:~# cp -rpf /etc/resolv.conf /etc/resolv.conf.orig
debian:~# echo "nameserver 8.8.8.7n nameserver 8.8.8.8 n" > /etc/resolv.conf;

I first create backu pof my resolv.conf under the name resolv.conf.orig just to make sure I can revert back to my old DNSes if I need them at some point.

If you prefer to use the OpenDNS services for some let’s say privacy reasons, you do it in the same manner as in the above commands, you only change the IP addresses. 4. Configure and use the OpenDNS public DNS services

debian:~# cp -rpf /etc/resolv.conf /etc/resolv.conf.orig
debian:~# echo "nameserver 208.67.222.222n nameserver 208.67.222.220 n" > /etc/resolv.conf;

Of course using Public DNS services has it’s disadvantages over the domain resolving speed up advantage.
One major issue is that Public DNS services are running on a top of a cloud and if you have red my previous article Cloud Computing a possible threat to users privacy and system administrator employment you might be agaist the idea of using a services which are powered by cloud.

The other primary concern is related to your SECURITY and a PRIVACY by using Public DNS networks, you risk that your Public DNS provider might use some DNS spoof techniques to mislead you and resolve you common domain names which usually resolve to let’s say 1.1.1.1 to let’s say 1.5.5.10

Even though this kind of practices on a side of a public DNS provider is not a likely scenario the possible implications of Public DNS providers using DNS forgery to fool you about domain names locations is a very serious issue.

As public DNS providers does contain again the good old philosophy of cloud computing embedded in themselves and they strive to become some kind of a standard which people might vote to adopt and use, the future implications of a wide adoption of Public DNS servers might be a terrible thing on internet users privacy!!!

Just think about a future scenario where we users of the Internet are forced to use a number of public DNS servers in order to use the Internet!
Usually a very huge companies are possessing the Public DNS services and do pay for the tech equipment required for building up the cluster clouds which provide the DNS services and therefore, if in the short future public DNS becomes a fashion and (God forbid!) a standard which shifts up the regular ISP DNS servers to resolve domains to IPs then it will be terrible.

The corporations which does own the Public DNS service/s might have a direct control over filtering and censoling information posted on any website on the internet.
Even worser if the world decides to adopt public DNS services somewhere in the future this means that large corporations owning the open dns cluster or clusters will be able to check each and every resolving made by any user on the net.
If you think closely such an information possessed by a company is not the best thing we want.

So let me close up this article, I’m not a fan and an evangelist who preaches the use of Public DNS services. Right on Contrary I do honestly hate the idea behind public DNS.
Nevertheless apart from my personal opinion I’m a practical person and using the public DNS servers every now and then when this will accelerate my access to the internet is still an option I do enjoy.

Maybe it’s time for a free software project (a tor like), which will provide users with an OpenDNS alternative which will run on hobbyist computers around the globe (just like with tor).

What’s rather funny is that the loud name OpenDNS is a big lie in reality OpenDNS is not opened it’s a company owned closed source service 😉