Symptoms: Low volume when playing all the media files or only some files.
- Soundcard drivers are not installed or buggy
- Improperly configured speaker settings
- Something set the Windows system sound level to a low value
- Files with Dolby Digital AC3 or DTS audio
- The file has poorly encoded audio
- Really poor quality speakers
- There's a bug in ffdshow audio decoding
1. Soundcard drivers are not installed or buggy
First of all, make sure you have the latest drivers for your soundcard installed.
2. Improperly configured speaker settings
Just respect the instructions on the Issues:No multichannel audio page.
3. Something set the Windows system sound level to a low value
Right click on the speaker icon in the system tray -> Open Volume Control -> make sure the slider on the leftmost column is set towards the top and not bottom.
4. Files with Dolby Digital AC3 or DTS audio
If low level volume only happens on some files, then it might be it's about files with AC3 or DTS audio.
The audio streams you are trying to play were meant to be played on a high quality audio system (most computer speakers and soundcards don't qualify as such) and as a result low level sounds are almost unhearable when listened to through computer speakers.
This is typically the case when trying to play a file with Dolby Digital AC3 or DTS audio streams ripped directly from DVD discs. See below for a little bit more information on why this happens.
Open ffdshow audio decoder configuration and do the following:
- make sure "Dynamic Range Compression" is checked for both AC3 and DTS on the Codecs page (click on them to see the option appear)
The best way to deal with this is to increase the sound volume by using the volume button on your speaker system when listening to media files that have Dolby Digital AC3 or DTS audio tracks.
If your sound volume button is already at max or you don't have one, then you could enable the ffdshow audio configuration Volume controls. Just check the Volume option in the list on the left. On that Volume panel, you can use the "Master volume" slider to increase the volume of all channels or use the slider for each channel individually. Please note this solution is not the best, since you may experience distorted sounds or clipping of loud sounds. Also note this will affect even files that sound well (those without AC3 or DTS audio streams), so make sure to uncheck the Volume opton after you're done playing a problematic file.
Finally, if not even the Volume option was satisfactory, then besides enabling the Volume option also check the "Normalize" option on the Volume tab. This will artificially increase the perceived sound level of low sounds making explosions and voices sound alike. Please note that this normalization will not always work properly: a common issue is to not hear what two people are speaking just after a scene in the movie where an explosion occured. Also, this will make all sounds have different sound levels than what they were intended to have, but it's better than hearing nothing, isn't it ? Don't forget to uncheck the "Normalize" option after you're done playing the problematic file or you'll experience normalization in all played media files.
5. The file has poorly encoded audio
Yes, this can happen. Blame the encoders. ^^ Jokes aside, just turn up the volume or follow all the advices when trying to play AC3 or DTS audio.
6. Really poor quality speakers
If low volume happens on all files all the time, then maybe it's because you have a really poor speaker system. If you're using a notebook, then please note they don't have quality speakers most of the time.
Try all the suggestions made for Dolby Digital AC3 and DTS but, in plus, keep the Volume option checked at all times and even the Normalize option checked at all times if you find that it's necessary.
7. There's a bug in ffdshow audio decoding
Unlikely but not impossible. If you do believe this is the case, have the file handy then come to the forums and state your problem. Most likely you'll have to provide a sample if we will consider this really is a decoding bug.
Additional information: Audio formats for high quality systems
Some types of audio streams (typically Dolby Digital AC3 and DTS found on DVDs) were meant to be played on high fidelity audio systems which are able to accurately reproduce low sounds as well as loud sounds very well for an immersive experience.
Sounds are produced inside the speakers by moving a membrane which in turn moves the air around creating the soundwaves you hear.
Low sounds (low amplitude sounds) like a breeze of wind through trees are reproduced by moving that membrane by a small amount creating low pressure sound waves.
Loud sounds (large amplitude sounds) like a thunder or explosions move that same membrane by wide movements creating high pressure sound waves just like a real thunder or explosion would do.
High quality speaker systems are able to reproduce both types of sounds just like you would hear them in real-life happening in front of your eyes, or should I say your ears.
Computer speakers systems, as well as other common speaker systems like those found on cd audio-players, radios, portable devices, etc. are unable to do so. Because of physical constraints, they are unable to reproduce low sounds. Such devices compensate for their speaker systems inability to reproduce low sounds by manipulating the sound before being output to the speakers and artificially enhancing the loudness level of low level sounds. As a result sounds that would have a great loudness gap between them in real-life (like between the human voice and the sound of an explosion) would be perceived to be equally loud or differ just by a minimal ammount when listend to through such a low-end audio system.
As a side-note, current day audio cds are already sold with such sound manipulation performed on them, so as to not decrease sales. If studios would not remaster the records they have like this, people trying to play their discs on cd-players or portable devices would complain of "low audio quality" (when in fact it's their players that are "low quality").
Additional information: The theory behind sound loudness, dynamic range and normalization
Read this nice description from the AC3filter docs: Theory
Please note however that the configuration advices found there are not quite the same for ffdshow, since there are code differences between ac3filter and the libraries used by ffdshow for ac3 & dts decoding. The implementation of "Normalization" is also kind of flawed in ac3filter as well as the libraries used by ffdshow so we'd advise against its usage.