Length of MP3 encoded with LAME

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C++

Am currently working on the encoding of pcm to mp3 using LAME but the length of the resulting mp3 is longer (and was able to isolate the part of the code causing this). The pcm is about 4:45 but when I encode with settings

lame_set_VBR(gfp, vbr_off);
lame_set_quality(gfp, 5);
lame_set_preset(gfp, 128);

the resulting mp3 length was about 11:30

when I encode with settings

lame_set_VBR(gfp, vbr_mtrh);
lame_set_VBR_quality(gfp, 5);

the resulting mp3 length was about 14:18

but when I encoded with settings

lame_set_VBR(gfp, vbr_abr);
lame_set_VBR_min_bitrate_kbps(gfp, 128);

the resulting mp3 length was correctly 4:45 (but I noticed when I increased the bitrate to 188, the length jumped up about 5sec to 4:50)


I dont really know what am doning wrong but it seems only abr is resulting the right length vbr and cbr are not!

UPDATE::::
when these mp3 are played, they played normal and stopped at 4:45 but the windows media player and their property(on windows) still reading those above lengths

UPDATE::: got the cbr settings working by removing the lame_set_preset settings. It's only the vbr settings that is returning incorrect length