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Merge branch 'fix-variable-blocksize-flac' into 'main'

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Fix parsing of variable blocksize FLAC streams

Closes #2682

See merge request gstreamer/gstreamer!4909
This commit is contained in:
Martijn van Beurden 2024-05-04 00:44:50 +00:00
parent 73c64e8182 02dadaa6ac
commit bff2218eac
1 changed files with 19 additions and 9 deletions
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28
subprojects/gst-plugins-good/gst/audioparsers/gstflacparse.c
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@ -559,19 +559,28 @@ gst_flac_parse_frame_header_is_valid (GstFlacParse * flacparse,
goto error;
}
/* Sanity check sample number against blocking strategy, as it seems
some files claim fixed block size but supply sample numbers,
rather than block numbers. */
if (blocking_strategy == 0 && flacparse->block_size != 0) {
/* The blocksize strategy bit was introduced in 2007. Sadly, many
* linux distros still ship a Flake version from before that. Flake
* is an alternative FLAC encoder that is able to produce variable
* blocksize files. This code here detects such files. See also:
* https://www.ietf.org/archive/id/draft-ietf-cellar-flac-08.html#name-addition-of-block-size-stra */
if (blocking_strategy == 0 && sample_number > 0) {
if (!flacparse->strategy_checked) {
if (block_size == sample_number) {
GST_WARNING_OBJECT (flacparse, "This file claims fixed block size, "
"but seems to be lying: assuming variable block size");
/* Minimum blocksize is 16, so if coded number jumps with 16 or
* more at the start of the file, this is probably a variable
* blocksize file */
if (flacparse->sample_number < sample_number
&& sample_number - flacparse->sample_number > 15) {
GST_INFO_OBJECT (flacparse,
"Variable blocksize file following pre-2007 FLAC format found");
flacparse->force_variable_block_size = TRUE;
flacparse->blocking_strategy = 1;
blocking_strategy = 1;
}
flacparse->strategy_checked = TRUE;
}
} else if (blocking_strategy == 1) {
flacparse->strategy_checked = TRUE;
}
/* documentation says:
@ -803,7 +812,6 @@ gst_flac_parse_handle_frame (GstBaseParse * parse,
guint next;
flacparse->offset = GST_BUFFER_OFFSET (buffer);
flacparse->blocking_strategy = 0;
flacparse->sample_number = 0;
GST_DEBUG_OBJECT (flacparse, "Found sync code");
@ -914,6 +922,9 @@ gst_flac_parse_handle_streaminfo (GstFlacParse * flacparse, GstBuffer * buffer)
flacparse->max_blocksize);
}
if (flacparse->min_blocksize < flacparse->max_blocksize)
flacparse->force_variable_block_size = TRUE;
if (!gst_bit_reader_get_bits_uint32 (&reader, &flacparse->min_framesize, 24))
goto error;
if (!gst_bit_reader_get_bits_uint32 (&reader, &flacparse->max_framesize, 24))
@ -1688,7 +1699,6 @@ gst_flac_parse_parse_frame (GstBaseParse * parse, GstBaseParseFrame * frame,
flacparse->min_framesize));
flacparse->offset = -1;
flacparse->blocking_strategy = 0;
flacparse->sample_number = 0;
res = GST_FLOW_OK;
}