investigate why some encoding test cases are failing

[mewmew]

investigate why some encoding test cases are failing

[mewmew]

From #66 (comment):

The fq tool by @wader has been invaluable to investigate the cause of diffs between input (decoding) and output (encoding) FLAC files.

To investigate a mismatch between input FLAC files and corresponding FLAC files produced by encode, do as follows.

0. switch to Git branch encode-lpc
1. uncomment the ioutil.WriteFile lines in TestEncode to output FLAC file (to /tmp/got.flac) when the contents of the round-trip test case mismatch.
2. uncomment a test case that is currently failing (e.g. testdata/59996.flac)
3. run go test -v -run TestEncode/testdata/59996.flac

=== RUN   TestEncode/testdata/59996.flac
    enc_test.go:206: "testdata/59996.flac": content mismatch;
    expected 66 4C 61 ... 7C A2 21 22 3B ... 80 32 2A,
    got      66 4C 61 ... 7C 62 21 12 3B ... 80 32 2A
                             ^     ^
                             |     |
                             |     |
                            DIFF  DIFF
--- FAIL: TestEncode (0.02s)
    --- FAIL: TestEncode/testdata/59996.flac (0.02s)

4. use fq to analyze the diff
   • 4a: analyze input FILE (source of truth): fq d -d flac testdata/59996.flac
   • 4b: analyze output FILE (produced by encode): fq d -d flac /tmp/got.flac

binary diff (using vbindiff) between input and output FLAC files

fq analysis of input FILE (source of truth)

fq d -d flac testdata/59996.flac

fq analysis of output FILE (produce by mewkiz/flac encoding)

fq d -d flac /tmp/got.flac

[mewmew]

From #66 (comment):

--input (orig):    testdata/59996.flac
++output (encode): /tmp/got.flac
 residual: (0b-0000000000000000011111100101101) -16173
 residual: (0b-0000000000000000011101101010011) -15187
 residual: (0b00000000000000000111101011001001) 31433
-residual: (0b-0000000000000000001110111110011) -7667
+residual: (0b-0000000000000000001110111110010) -7666
-residual: (0b00000000000000000110001000010010) 25106
+residual: (0b00000000000000000110001000010001) 25105
-residual: (0b00000000000000000010001110110100) 9140
+residual: (0b00000000000000000010001110110101) 9141
-residual: (0b-0000000000000000110000000101110) -24622
+residual: (0b-0000000000000000110000000110000) -24624
-residual: (0b00000000000000000001000011000000) 4288
+residual: (0b00000000000000000001000011000010) 4290
-residual: (0b00000000000000000110101101001001) 27465
+residual: (0b00000000000000000110101101000110) 27462
-residual: (0b-0000000000000000111100011100001) -30945
+residual: (0b-0000000000000000111100011011110) -30942
-residual: (0b00000000000000000111111110100011) 32675
+residual: (0b00000000000000000111111110100000) 32672
-residual: (0b-0000000000000000101000111001011) -20939
+residual: (0b-0000000000000000101000111001001) -20937
-residual: (0b-0000000000000000011011001011101) -13917
+residual: (0b-0000000000000000011011001011110) -13918
 residual: (0b00000000000000001000100101110011) 35187
 residual: (0b-0000000000000001101011111001001) -55241

There seem to be a small diff in the residual between the original input FLAC file and the encoded output FLAC file.

Still not sure why. Anyone who may have an idea? : )

[mewmew]

Fixed by 70d4ace.