On Sun, 22 Jan 2012 12:44:14 +0000 (GMT), Brian Bailey
> I'm curious about the relative acoustic performance of VLC,
> WMP, their codecs and the way they work.
Your best bet here would be to find a forum relevant to technical
discussion of the internal workings of codecs.
I 99% of cases, SMPlayer "just works". I did have a multilingual
EN/JP MKV that played silent, but picking a different MKV splitter
This weeks episode of "Moretsu Pirates" failed on SMPlayer, but
played on VLC. There are many variations of what might seem to be the
> I assume, that each player refers to a library of codecs, which, I
> assume, decompress the various file formats that are thrown at them.
In general, yes. But note that "codec" is a very misunderstood word.
Meaning "COder/DECoder", is it correct to call a playback-only piece
of software a codec?
Waters further muddied by Philips who refer to their AIC23 chip as a
codec. It takes analogue audio and converts it to a McBSP data
stream, and vice versa, so technically their use of the term is
correct, though most people would think of a lump of software as a
> You referred to a specific codec
I did? I thought I referred to a movie player for a specific file
If you look in SMPlayer's menus, File information or such, there is a
way to pick the "codec" you like. You'll notice there are three or
four for H.264 video (much is from ffmpeg).
> Stay with me, I am trying to gain
> some understanding of the way things work.
At its most basic, a file is a chunked set of stream data - in other
words, you have a big stream of data that is split into bits so there
can be some relationship between which bit of audio goes which which
bit of video. This is not necessary, one stream could follow another,
and on an AVI sitting on a harddisc it'll work okay, but the same on
a CD-R would be a disaster of endless seeks.
Note, by "stream" I mean a large sequence of data that describes a
picture or a sound. This isn't the same as "streaming".
Note, also, we have not yet mentioned the encoding.
So, you have this arrangement that is video and audio like
The next step is a "splitter" (also known as a "demuxer"). This
understands the file, but not the encoding. It's job is to separate
the audio data and video data into unique blocks of data. Typically
the decoder for each will work as an independent thread, so the video
decoder gets the video data, and so on. While file formats are
broadly similar (3gp vs MKV vs AVI vs mp4 vs flv...), they are not
compatible *even* *if* the data within is the same.
The final step is the decoder, what most think of as the codec. It
takes H.263 (XviD etc) or whatever and pastes it to the screen, while
a different decoder takes the mp3 (etc) and dumps it on the sound
driver. The end result? A movie to watch.
> I've used WMP and have no difficulty in rejecting it.
Correction - you've used WMP and it had no difficulty in rejecting
your files if they were in any way "unusual".
> I was surprised to find that, in this instance, that there are a
> number of options for decoding mp3 files in each player.
Not a surprise. With a hardware player you get what you are given.
But there is no such thing as a one-size-fits-all. On my phone, for
example, I like strongly emphasised bass to compensate for the use of
> I assume that the skill in designing a player is in enabling the
> the /best/ codec for the file in question.
Difficult. mp3 is a lossy codec, and you will find that for identical
settings, different encoders produce different results. There is a
lot of technology hidden behind phrases like "psychoacoustic" - in
essense, the decision of what is okay to throw away to make something
that "sounds the same" (as the input).
There are also differences like true stereo vs joint stereo (mono
channel plus a list of differences used to reconstruct stereo).
> Anyway, I had downloaded an mp3 file of the Schubert quintet. The
> play-back through SMPlayer was barely acceptable whereas the
> through VLC was entirely credible and alive.
Where might I find a copy of this to try it on my setup?
Check also your player settings (outside of the decoder choice). Is
it using the correct driver, or the Windows WAV fall-back? My system
has eight choices, I currently use "dsound". I have my SMPlayer set
to equalise audio, downmixed to stereo for headphones. Windows itself
has been told to mix for headphones.
This is important as different people will perceive sounds in
different ways. I could always tell Eagle FM (Guildford) on the dial
as the sound was very warm, like a valve radio, although technically
they must have been messing with it. It sounded better that way, a
purist might disagree. Then there is a battle to get the best output
from the smallest number of bits, and reconstruct that to an
acceptable representation of the original. Then there are technical
issues - domestic kit hasn't yet entirely caught on to 24 bit
sampling, so the file might be 24 bit, the audio output hardware
might be 24 bit, but the driver in the middle might chuck away some
of that, being stuck in a 16 bit world. It sounds silly, but then so
does a computer that tries to play everything at 48k sampling rate...
To be honest, however, if you appreciate music, you might find a
lossless format is better than mp3. Failing that, AAC at a high
enough bitrate (288kbit), and as a *last* resort, mp3 at 320kbit.
That's why I'd never buy music from Deezer, they were offering mp3 at
a mere 128kbit - I don't even consider that adequate for stuff I
record off the telly!
> What is being looked for in the file format to enable the /correct/
> selection of a codec?
Probably just a lookup table linking data type to what works on most
platforms. Just looking, mp3 is MPEG layer 3, which means I can pick
ffmp3, mp3, mad, or mp3acm. There might be others. The default is
> Could you give some clue as to what is going on here, please.
Tell me where I can get the file and I'll try it on SMPlayer, VLC,
and WinAMP (with headphones) on my machine. Note, incidentally, that
the first two are designed to play video - audio only playback might
be seen as an "also" feature (ie, where's the eq? the stereo balance,