Howdy Steve,

In case Mark's reply didn't adequately solve your problem:

> I'd like to know your point of view on the "Free format" that
> lame generates.
> I've created a free format file with 'lame --freeformat -b 62
> file.au". I'm using lame 3.86beta on Win32 compiled locally
> using MinGW32 with Libsndfile and full speed optimization
> (all I found usefull in the GCC doc). And it usually works fine.
>
> But with free format, it sometimes generate half frames. The
> file seems to have the following characteristics :
> MPEG_VERSION        MPEG_2
> MPEG_LAYER          LAYER_III
> PROT_BIT            0
> BIT_RATE            1
> SAMPLE_FREQ         22050
> SAMPLES_PER_FRAME   1152
> PAD_BIT             0
> PRIV_BIT            0
> CHANNEL             JOINT_STEREO
> MODE_EXTENSION      Intensity OFF / MS ON
> ID3V2               0
> FRAME_LENGTH        405
> COPYRIGHT           0
> ORIGINAL            1
> EMPHASIS            NONE
> CHECK_STATE         1
> BIN_STRING          11111111111100110000000001100100
>
> BIT_RATE = 1 means free format.

This seems kinda confusing -- why use 1 to indicate free when MPEG uses 0?

> I've checked the file in hexadecimal, and sometimes I get
> frame header at 202 bytes from the previous instead of 405.
> So I was wondering if this is not a bug of lame or if the
> free format allow this (but I don't think so).
>
> The other possibility is that the real frame size is 202
> bytes, but then would some of the frames would be separated
> by 405 bytes ?

Doing the math:

(576 samp/gr * 1 gr/fr * 62000 bps)/(8 bit/byte * 22050 samp/s) = 202.4
byte/fr
  layer-III    MPEG-2     bitrate    conversion    samp freq

Given that this is non-integral, padding will sometimes occur.  When the
padding bit is cleared, the frame size will be 202, and when it is set, it
will be 203.  Thus, I surmise that there are no 405 byte frames - you just
aren't tracking syncs correctly.  Are you factoring in the padding bit?

Hope that helps,
Alex

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