74 lines
3.2 KiB
Diff
74 lines
3.2 KiB
Diff
Author: Arthur Taylor <art@ified.ca>
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Reason: The minimal possible MPEG file contains no headers or identification
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other than the brief sync header. This header is only 3 bytes, and is quite
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prone to false-positives. Particularly raw PCM can look like a sync header.
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As such, move detection of 'naked' MPEG files in guess_file_type()
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to the very last test. Give more weight to a sync header if it
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follows an ID3 tag.
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See https://github.com/libsndfile/libsndfile/pull/898
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Upstream: yes
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--- a/src/sndfile.c
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+++ b/src/sndfile.c
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@@ -2771,6 +2771,17 @@ format_from_extension (SF_PRIVATE *psf)
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return format ;
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} /* format_from_extension */
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+static int
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+identify_mpeg (uint32_t marker)
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+{ if ((marker & MAKE_MARKER (0xFF, 0xE0, 0, 0)) == MAKE_MARKER (0xFF, 0xE0, 0, 0) && /* Frame sync */
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+ (marker & MAKE_MARKER (0, 0x18, 0, 0)) != MAKE_MARKER (0, 0x08, 0, 0) && /* Valid MPEG version */
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+ (marker & MAKE_MARKER (0, 0x06, 0, 0)) != MAKE_MARKER (0, 0, 0, 0) && /* Valid layer description */
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+ (marker & MAKE_MARKER (0, 0, 0xF0, 0)) != MAKE_MARKER (0, 0, 0xF0, 0) && /* Valid bitrate */
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+ (marker & MAKE_MARKER (0, 0, 0x0C, 0)) != MAKE_MARKER (0, 0, 0x0C, 0)) /* Valid samplerate */
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+ return SF_FORMAT_MPEG ;
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+ return 0 ;
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+} /* identify_mpeg */
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+
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static int
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guess_file_type (SF_PRIVATE *psf)
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{ uint32_t buffer [3], format ;
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@@ -2872,13 +2883,6 @@ guess_file_type (SF_PRIVATE *psf)
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if (buffer [0] == MAKE_MARKER ('R', 'F', '6', '4') && buffer [2] == MAKE_MARKER ('W', 'A', 'V', 'E'))
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return SF_FORMAT_RF64 ;
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- if ((buffer [0] & MAKE_MARKER (0xFF, 0xE0, 0, 0)) == MAKE_MARKER (0xFF, 0xE0, 0, 0) && /* Frame sync */
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- (buffer [0] & MAKE_MARKER (0, 0x18, 0, 0)) != MAKE_MARKER (0, 0x08, 0, 0) && /* Valid MPEG version */
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- (buffer [0] & MAKE_MARKER (0, 0x06, 0, 0)) != MAKE_MARKER (0, 0, 0, 0) && /* Valid layer description */
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- (buffer [0] & MAKE_MARKER (0, 0, 0xF0, 0)) != MAKE_MARKER (0, 0, 0xF0, 0) && /* Valid bitrate */
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- (buffer [0] & MAKE_MARKER (0, 0, 0x0C, 0)) != MAKE_MARKER (0, 0, 0x0C, 0)) /* Valid samplerate */
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- return SF_FORMAT_MPEG ;
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-
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if (buffer [0] == MAKE_MARKER ('I', 'D', '3', 2) || buffer [0] == MAKE_MARKER ('I', 'D', '3', 3)
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|| buffer [0] == MAKE_MARKER ('I', 'D', '3', 4))
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{ psf_log_printf (psf, "Found 'ID3' marker.\n") ;
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@@ -2887,6 +2891,10 @@ guess_file_type (SF_PRIVATE *psf)
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return 0 ;
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} ;
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+ /* ID3v2 tags + MPEG */
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+ if (psf->id3_header.len > 0 && (format = identify_mpeg (buffer [0])) != 0)
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+ return format ;
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+
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/* Turtle Beach SMP 16-bit */
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if (buffer [0] == MAKE_MARKER ('S', 'O', 'U', 'N') && buffer [1] == MAKE_MARKER ('D', ' ', 'S', 'A'))
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return 0 ;
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@@ -2898,10 +2906,16 @@ guess_file_type (SF_PRIVATE *psf)
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if (buffer [0] == MAKE_MARKER ('a', 'j', 'k', 'g'))
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return 0 /*-SF_FORMAT_SHN-*/ ;
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- /* This must be the last one. */
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+ /* This must be (almost) the last one. */
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if (psf->filelength > 0 && (format = try_resource_fork (psf)) != 0)
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return format ;
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+ /* MPEG with no ID3v2 tags. Only have the MPEG sync header for
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+ * identification and it is quite brief, and prone to false positives.
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+ * Check for this last, even after resource forks. */
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+ if (psf->id3_header.len == 0 && (format = identify_mpeg (buffer [0])) != 0)
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+ return format ;
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+
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return 0 ;
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} /* guess_file_type */
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