amix scales each input’s volume by 1/n where n = no. of active inputs. This is evaluated for each audio frame. So when an input drops out, the volume of the remaining inputs is scaled by a smaller amount, hence their volumes increase. Changing the dropout_transition for all earlier inputs, as suggested in other answers, … Read more
Use the silenceremove filter. This removes silence from the audio track only – it will leave the video unedited, i.e., things will go out of sync Its arguments are a little cryptic. An example ffmpeg -i input.mp3 -af silenceremove=1:0:-50dB output.mp3 This removes silence at the beginning (indicated by the first argument 1) with minimum length … Read more
The following command will mute two sections: between 5-10s and 15-20s: ffmpeg -i video.mp4 -af “volume=enable=”between(t,5,10)”:volume=0, volume=enable=”between(t,15,20)”:volume=0″ … Description: -af is the audio filter. It works by specifying multiple volume filters that are enabled/disabled at the specified time. volume=enable=”between(t,5,10)”:volume=0 means use a volume filter that gets enabled between 5 and 10 seconds and sets the … Read more
You will have heard, that audio signals are represented by some kind of wave. If you have ever seen this wave diagrams with a line going up and down — that’s basically what’s inside those files. Take a look at this file picture from http://en.wikipedia.org/wiki/Sampling_rate You see your audio wave (the gray line). The current … Read more
Physically, as you probably know, audio is a vibration. Typically, we’re talking about vibrations of air between approximitely 20Hz and 20,000Hz. That means the air is moving back and forth 20 to 20,000 times per second. If you measure that vibration and convert it to an electrical signal (say, using a microphone), you’ll get an … Read more
All the previous answers are correct if you want a technically accurate or scientifically valuable answer. But if you just want a general estimation of comparative loudness, like if you want to check whether the dog is barking or whether a baby is crying and you want to specify the threshold in dB, then it’s … Read more
In Windows Vista and beyond, you can use the device arrival and removal notifications and retrieve the endpoint formfactor to determine if the manufacturer of your audio solution considers a particular endpoint a “headphone”. Before Vista there was no way of determining this information.
Can you post the headers sent by the server both with and without the PHP script? I’m wondering if the PHP script is sending a different Content-Type than serving the files normally. It would also be a good idea to specify the type attribute on the source elements, so the browser does not have to … Read more
stereo + stereo → stereo Normal downmix Use the amix filter: ffmpeg -i input0.mp3 -i input1.mp3 -filter_complex amix=inputs=2:duration=longest output.mp3 Or the amerge filter: ffmpeg -i input0.mp3 -i input1.mp3 -filter_complex amerge=inputs=2 -ac 2 output.mp3 Downmix each input into specific output channel Use the amerge and pan filters: ffmpeg -i input0.mp3 -i input1.mp3 -filter_complex “amerge=inputs=2,pan=stereo|c0<c0+c1|c1<c2+c3” output.mp3 mono … Read more
David’s answer is correct that just concatenating the files will leave ID3 tags scattered inside (although this doesn’t normally affect playback, so you can do “copy /b” or on UNIX “cat a.mp3 b.mp3 > combined.mp3” in a pinch). However, mp3wrap isn’t exactly the right tool to just combine multiple MP3s into one “clean” file. Rather … Read more