flac dev - Apr 2012 - Writing seektable using libFLAC++

Hi! I've been using a little C++ program I've written to encode flac
files. The program does this in the usual way (I think), by inheriting a class
from FLAC::Encoder::File, and passing it chunks of raw samples through
process_interleaved()... Anyway, the program works beautifully, and I've now
decided to try and add some metadata to the encoded flacs. Eventually, there
will be vorbis comments, but right now I'm just trying to add a seektable.
From some code examples I've managed to get it working  using the libFLAC C
API like this:

  FLAC__StreamMetadata *md[1];
  md[0] = FLAC__metadata_object_new(FLAC__METADATA_TYPE_SEEKTABLE);  // THIS
LEAKS
  FLAC__metadata_object_seektable_template_append_spaced_points(md[0], 13,
d_bytestotal / 4);
  FLAC__metadata_object_seektable_template_sort(md[0], true);
  set_metadata(md, 1);

Now, I have several questions:

1. Most importantly: How can I get this to work with the libFLAC++ API? Do I not
_need_ the template-methods, and are they not missing from the C++ API? I've
also tried getting just half the metadata code from the C++ API and using the C
API for the template-functions, like this:

  FLAC::Metadata::Prototype *md[1];
  FLAC__StreamMetadata *seektable =
FLAC__metadata_object_new(FLAC__METADATA_TYPE_SEEKTABLE);
  FLAC__metadata_object_seektable_template_append_spaced_points(seektable, 13,
d_bytestotal / 4);
  FLAC__metadata_object_seektable_template_sort(seektable, true);
  md[0] = new FLAC::Metadata::SeekTable(seektable);
  set_metadata(md, 1);

But that does not seem to work. Checking md[0]->type(), and
md[0]->is_valid() and md[0]->is_legal() all return expected values, but
the resulting flac has no seektable, but instead a 0-length metadata block of
type 56 (UNKNOWN). So what am I doing wrong? And can I get rid of the C API
calls altogether? Also, as you can see I'm arbitrarily creating 13
seekpoints, this is just for testing. But what is a good amount of seekpoints,
how does the official flac binary determine a default?

2. I noticed while reading the source that all FLAC::Metadata::Prototype child
classes have default constructors, that seem to do what you'd expect. They
are not mentioned in the API docs (for example:
http://flac.sourceforge.net/api/classFLAC_1_1Metadata_1_1SeekTable.html). Can
this be considered a bug?

3. Assuming the FLAC__metadata_object_seektable_template_* functions are
necessary for creating a proper seektable, and that these functions don't
exist in the C++ API, would it be appreciated if I wrote some wrappers for these
functions as members of the FLAC::Metadata::Seektable class? I'm assuming
these functions would just be one-liners, so I should be capable and willing to
do that. The same goes for all other FLAC__metadata_object_* functions not
already wrapped in the appropriate FLAC::Metadata::Prototype children.

Sorry for the long message... but thanks for reading!

bepaald

Well, I have to apologize, we can disregard the most important part of my
previous mail. The code mentioned in that one does in fact work fine when
compiled against current git. I had only compiled against current (but old)
stable release when I wrote that, which suffered from a bug (commit
1649c4ab3c08d95fb1056d73d8809fa77d4976dc). And I can, indeed, get rid of the C
API calls altogether like this:

d_md = new FLAC::Metadata::Prototype *[d_metadatasize];
d_md[d_metadatasize - 1] = new FLAC::Metadata::SeekTable;
for (int i = 0; i < numseekpoints; ++i)
  reinterpret_cast<FLAC::Metadata::Seektable
*>(d_md[0])->insert_point(i, {i * spacing, 0, 0});

It would, however, still be more natural (and sometimes more efficient) to be
able to call 'Seektable::resize_points()' and
'Seektable::set_point()' (as is done in
FLAC__metadata_object_seektable_template_append_spaced_points_by_samples()), or
even to call 'template_append_spaced_points_by_samples()' directly on
the Seektable object so we can write somethign like the following:

d_md = new FLAC::Metadata::Prototype *[d_metadatasize];
d_md[d_metadatasize - 1] = new FLAC::Metadata::SeekTable;
reinterpret_cast<FLAC::Metadata::Seektable
*>(d_md[0])->template_append_spaced_points_by_samples(samples,
total_samples);

Which would be more or less identical to how it's done in the C API. I am
still willing to create those functions in libFLAC++, but I would like to hear
if there's any chance they'll make it in (assuming they are written
correctly and working). Maybe there is some reason only a few functions from
FLAC/metadata.h are currently reproduced in the C++ API...

thanks,
Bas Timmer