[FFmpeg-devel] [PATCH] use new metadata API in realmedia

[Aurelien Jacobs]

On Tue, 17 Feb 2009 01:42:37 +0100
Michael Niedermayer <michaelni at gmx.at> wrote:

> On Tue, Feb 17, 2009 at 01:15:04AM +0100, Aurelien Jacobs wrote:
> > Hi,
> > 
> > Attached patch converts rm muxer and demuxer to the new metadata API.
> > 
> > Aurel
> > Index: libavformat/rmenc.c
> > ===================================================================
> > --- libavformat/rmenc.c	(revision 17387)
> > +++ libavformat/rmenc.c	(working copy)
> > @@ -70,7 +70,18 @@
> >      const char *desc, *mimetype;
> >      int nb_packets, packet_total_size, packet_max_size, size, packet_avg_size, i;
> >      int bit_rate, v, duration, flags, data_pos;
> > +    const char *title, *author, *copyright, *comment;
> > +    AVMetadataTag *tag;
> >  
> > +    tag = av_metadata_get(ctx->metadata, "title"    , NULL, 0);
> > +    title     = tag ? tag->value : "";
> > +    tag = av_metadata_get(ctx->metadata, "author"   , NULL, 0);
> > +    author    = tag ? tag->value : "";
> > +    tag = av_metadata_get(ctx->metadata, "copyright", NULL, 0);
> > +    copyright = tag ? tag->value : "";
> > +    tag = av_metadata_get(ctx->metadata, "comment"  , NULL, 0);
> > +    comment   = tag ? tag->value : "";
> > +
> >      start_ptr = s->buf_ptr;
> >  
> >      put_tag(s, ".RMF");
> > @@ -123,14 +134,14 @@
> >      /* comments */
> >  
> >      put_tag(s,"CONT");
> > -    size = strlen(ctx->title) + strlen(ctx->author) + strlen(ctx->copyright) +
> > -        strlen(ctx->comment) + 4 * 2 + 10;
> > +    size = strlen(title) + strlen(author) + strlen(copyright) +
> > +        strlen(comment) + 4 * 2 + 10;
> >      put_be32(s,size);
> >      put_be16(s,0);
> > -    put_str(s, ctx->title);
> > -    put_str(s, ctx->author);
> > -    put_str(s, ctx->copyright);
> > -    put_str(s, ctx->comment);
> > +    put_str(s, title);
> > +    put_str(s, author);
> > +    put_str(s, copyright);
> > +    put_str(s, comment);
> 
> for(i=0; i<FF_ARRAY_ELEMS(meta); i++)
>     put_str(s, av_metadata_get(ctx->metadata, meta[i], NULL, 0));

This is not exactly as simple, because:
 - av_metadata_get() don't return a char*
 - av_metadata_get() can return NULL
So this would looks more like:
  for(i=0; i<FF_ARRAY_ELEMS(meta); i++) {
     AVMetadataTag *tag = av_metadata_get(ctx->metadata, meta[i],NULL,0);
     put_str(s, tag ? tag->value : "");
  }
But even with this, we are still left we the size calculation above.
It could be done with an additionnal loop, like:
  size =  4 * 2 + 10;
  for(i=0; i<FF_ARRAY_ELEMS(meta); i++) {
     AVMetadataTag *tag = av_metadata_get(ctx->metadata, meta[i],NULL,0);
     size += tag ? strlen(tag->value) : 0;
  }
So this starts looking not so much better than my initial version.
Still, attached patch contains those modifications.

An obvious alternative would be to use a dyn_buf, so that we can
use a single loop, but this would be even more ugly IMO:
  char *buf;
  int size;
  int ret = url_open_dyn_buf(&pb);
  if(ret < 0)
    return ret;
  size =  4 * 2 + 10;
  for(i=0; i<FF_ARRAY_ELEMS(meta); i++) {
     AVMetadataTag *tag = av_metadata_get(ctx->metadata, meta[i],NULL,0);
     char *value = tag ? tag->value : "";
     size += strlen(value);
     put_str(s, value);
  }
  size = url_close_dyn_buf(pb, &buf);
  put_be32(s,size);
  put_be16(s,0);
  put_buffer(s, buf, size);
  av_free(buf);

> >      for(i=0;i<ctx->nb_streams;i++) {
> >          int codec_data_size;
> > Index: libavformat/rmdec.c
> > ===================================================================
> > --- libavformat/rmdec.c	(revision 17387)
> > +++ libavformat/rmdec.c	(working copy)
> > @@ -72,6 +72,13 @@
> >      get_strl(pb, buf, buf_size, get_byte(pb));
> >  }
> >  
> > +static void get_tag(AVFormatContext *s, int len, const char *name)
> > +{
> > +    char buf[1024];
> > +    get_strl(s->pb, buf, sizeof(buf), len);
> > +    av_metadata_set(&s->metadata, name, buf);
> > +}
> > +
> >  RMStream *ff_rm_alloc_rmstream (void)
> >  {
> >      RMStream *rms = av_mallocz(sizeof(RMStream));
> > @@ -95,10 +102,10 @@
> >      if (((version >> 16) & 0xff) == 3) {
> >          int64_t startpos = url_ftell(pb);
> >          url_fskip(pb, 14);
> > -        get_str8(pb, s->title, sizeof(s->title));
> > -        get_str8(pb, s->author, sizeof(s->author));
> > -        get_str8(pb, s->copyright, sizeof(s->copyright));
> > -        get_str8(pb, s->comment, sizeof(s->comment));
> > +        get_tag(s, get_byte(pb), "title");
> > +        get_tag(s, get_byte(pb), "author");
> > +        get_tag(s, get_byte(pb), "copyright");
> > +        get_tag(s, get_byte(pb), "comment");
> 
> for()
>     get_tag(s, ...meta_tag_name_whatever[i]);

OK.

Updated patch attached.

Aurel
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