> X-Authentication-Warning: geek.rcc.se: majordom set sender to
>[EMAIL PROTECTED] using -f
> From: "Steve Lhomme" <[EMAIL PROTECTED]>
> Date: Sat, 19 Aug 2000 16:06:48 +0200
>
> 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.
>
> 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 ?
>
> any opinions welcomed (I can make the files available if necessary)
>
> thx
>
If sample_freq < 32khz, samples per frame = 576 (not 1152)!
This the the so-called 'LSF' extension of MPEG:
32khz - 48khz: MPEG1 Layer 3 1152 samples per frame
16khz - 24khz: MPEG2 layer 3 576 samples per frame
8khz - 12khz: MPEG2.5 layer 3 576 samples per frame.
Mark
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