[ lame-Bugs-3475583 ] lame+libsndfile reads and decodes input twice

Bugs item #3475583, was opened at 2012-01-18 09:57
Message generated for change (Tracker Item Submitted) made by lvqcl
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: lvqcl (lvqcl)
Assigned to: Nobody/Anonymous (nobody)
Summary: lame+libsndfile reads and decodes input twice

Initial Comment:
LAME now calls "sf_command(gs_pSndFileIn, SFC_SET_SCALE_FLOAT_INT_READ, NULL, SF_TRUE)" but it seems that libsndfile reads and decodes an input file during this call (to determine its peak value). Then LAME reads the input file again to encode it to MP3.

IMHO it is better to remove this call and maybe replace sf_read_int(...) with the following:

float   insampflt[2 * 1152];
...
...
samples_read = sf_read_float(global.snd_file, insampflt, num_channels * samples_to_read);
for(i=0; i<samples_read; i++)
{
    float x = insampflt[i] * ((float)INT_MAX + 1.0);
    if (x > (float)INT_MAX) x = (float)INT_MAX;
    else if (x < (float)INT_MIN) x = (float)INT_MIN;
    insamp[i] = (int)x;
}

Usually it will result in double conversion (int->float->int) but it is better than reading+decoding an input file twice.

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