[asterisk-bugs] [JIRA] (ASTERISK-20984) Audible clicks when playing sox encoded au file with STREAM FILE AGI command

[Roman S. (JIRA)]

     [ https://issues.asterisk.org/jira/browse/ASTERISK-20984?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Roman S. updated ASTERISK-20984:
--------------------------------

    Comment: was deleted

(was: Please disregard my previous patch, it has errors. Check current one.)
    
> Audible clicks when playing sox encoded au file with STREAM FILE AGI command
> ----------------------------------------------------------------------------
>
>                 Key: ASTERISK-20984
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-20984
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Formats/format_pcm
>    Affects Versions: SVN, 1.8.20.0
>            Reporter: Roman S.
>            Severity: Trivial
>         Attachments: asterisk-1.8.20.0-au-clicks-2.diff
>
>
> This is duplicate of ASTERISK-12703 (which is closed, but doesn't solve described issue fully). Initial issue is reproduced with STREAM FILE AGI command and sox encoded au file.
> Detailed description:
> {noformat}
> > soxi no.au 
> Input File     : 'no.au'
> Channels       : 1
> Sample Rate    : 8000
> Precision      : 14-bit
> Duration       : 00:00:00.60 = 4831 samples ~ 45.2906 CDDA sectors
> File Size      : 4.88k
> Bit Rate       : 64.6k
> Sample Encoding: 8-bit u-law
> Comment        : 'Processed by SoX'
> {noformat}
> {noformat}
> > xxd no.au  | head -n 5
> 0000000: 2e73 6e64 0000 002c 0000 12df 0000 0001  .snd...,........
> 0000010: 0000 1f40 0000 0001 5072 6f63 6573 7365  ... at ....Processe
> 0000020: 6420 6279 2053 6f58 0000 0000 ffff ff7e  d by SoX.......~
> 0000030: feff ffff ff7e 7e7e ffff ffff ffff ffff  .....~~~........
> 0000040: 7efe 7eff ffff fffe 7eff ffff ffff ffff  ~.~.....~.......
> {noformat}
> formats/format_pcm.c
> {noformat}
> 282 static int check_header(FILE *f)
> 300         hdr_size = ltohl(header[AU_HDR_HDR_SIZE_OFF]);
> 301         if (hdr_size < AU_HEADER_SIZE) {
> 302                 hdr_size = AU_HEADER_SIZE;
> {noformat}
> Header size can be larger then default AU_HEADER_SIZE (24 bytes). For mentioned no.au it's 44:
> {noformat}
> 300             hdr_size = ltohl(header[AU_HDR_HDR_SIZE_OFF]);
> (gdb)
> 301             if (hdr_size < AU_HEADER_SIZE) {
> (gdb) p hdr_size
> $6 = 44
> {noformat}
> But au_seek() disregarding determined in check_header() value uses default size (AU_HEADER_SIZE = 24).
> {noformat}
> 399         off_t min = AU_HEADER_SIZE, max, cur;
> 422         if (whence == SEEK_SET)
> 423                 offset = bytes + min;
> {noformat}
> This causes audible clicks at the beginning of each such .au file.
> Issue is reproduced with AGI STREAM FILE command because of:
> {noformat}
> 1933 static int handle_streamfile(struct ast_channel *chan, AGI *agi, int argc, const char * const argv[])
> 1959         ast_seekstream(fs, 0, SEEK_END);
> 1960         max_length = ast_tellstream(fs);
> 1961         ast_seekstream(fs, sample_offset, SEEK_SET);
> {noformat}
> Playback app. doesn't have such clicks because of direct file seeking - pos = ftello() -> fseeko(END) -> ftello() -> fseeko(pos) - file pointer returns to the same file position (44 instead of 24).

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