[FFmpeg-devel] [PATCH v2] ffprobe: Add a few common disposition cases

[Stefano Sabatini]

On date Tuesday 2012-09-18 16:12:01 -0400, Derek Buitenhuis encoded:
> This info is crucial in knowing which stream to pick in an
> automated setup.
> 
> Signed-off-by: Derek Buitenhuis <derek.buitenhuis at gmail.com>
> ---
> Since these must be printed unconditionally, I've kept attached_pic
> under the video case.
> ---
>  doc/ffprobe.xsd |    3 +++
>  ffprobe.c       |    6 ++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/doc/ffprobe.xsd b/doc/ffprobe.xsd
> index c9213de..b4887ae 100644
> --- a/doc/ffprobe.xsd
> +++ b/doc/ffprobe.xsd
> @@ -100,6 +100,8 @@
>        <xsd:attribute name="codec_tag"        type="xsd:string" use="required"/>
>        <xsd:attribute name="codec_tag_string" type="xsd:string" use="required"/>
>        <xsd:attribute name="extradata"        type="xsd:string" />
> +      <xsd:attribute name="default"          type="xsd:int" use="required"/>
> +      <xsd:attribute name="forced"           type="xsd:int" use="required"/>
>  
>        <!-- video attributes -->
>        <xsd:attribute name="width"                type="xsd:int"/>
> @@ -110,6 +112,7 @@
>        <xsd:attribute name="pix_fmt"              type="xsd:string"/>
>        <xsd:attribute name="level"                type="xsd:int"/>
>        <xsd:attribute name="timecode"             type="xsd:string"/>
> +      <xsd:attribute name="attached_pic"         type="xsd:int"/>
>  
>        <!-- audio attributes -->
>        <xsd:attribute name="sample_fmt"       type="xsd:string"/>
> diff --git a/ffprobe.c b/ffprobe.c
> index a0aee83..771c11d 100644
> --- a/ffprobe.c
> +++ b/ffprobe.c
> @@ -1665,6 +1665,10 @@ static void show_stream(WriterContext *w, AVFormatContext *fmt_ctx, int stream_i
>          print_str("codec_tag_string",    val_str);
>          print_fmt("codec_tag", "0x%04x", dec_ctx->codec_tag);
>  
> +        /* Print useful disposition */
> +        print_int("default", !!(stream->disposition & AV_DISPOSITION_DEFAULT));
> +        print_int("forced", !!(stream->disposition & AV_DISPOSITION_FORCED));
> +
>          switch (dec_ctx->codec_type) {
>          case AVMEDIA_TYPE_VIDEO:
>              print_int("width",        dec_ctx->width);
> @@ -1693,6 +1697,8 @@ static void show_stream(WriterContext *w, AVFormatContext *fmt_ctx, int stream_i
>              } else {
>                  print_str_opt("timecode", "N/A");
>              }
> +            print_int("attached_pic",
> +                      !!(stream->disposition & AV_DISPOSITION_ATTACHED_PIC));
>              break;

After looking at the code, I see that disposition can have many
possibly useful values:

#define AV_DISPOSITION_DEFAULT   0x0001
#define AV_DISPOSITION_DUB       0x0002
#define AV_DISPOSITION_ORIGINAL  0x0004
#define AV_DISPOSITION_COMMENT   0x0008
#define AV_DISPOSITION_LYRICS    0x0010
#define AV_DISPOSITION_KARAOKE   0x0020
#define AV_DISPOSITION_FORCED    0x0040
#define AV_DISPOSITION_HEARING_IMPAIRED  0x0080  /**< stream for hearing impaired audiences */
#define AV_DISPOSITION_VISUAL_IMPAIRED   0x0100  /**< stream for visual impaired audiences */
#define AV_DISPOSITION_CLEAN_EFFECTS     0x0200  /**< stream without voice */
#define AV_DISPOSITION_ATTACHED_PIC      0x0400

Having a single field for each separate value is going to be pretty
verbose and would require manual updates, so I wonder what's the best
way to show flags in this case and in general (may be useful to show
codec properties for example).

It could be rendered as a string, something like:
disposition=default+attached_pic+forced

On the other hand we don't have a clean way to convert numerical
flags to a string (we could add options support to AVStream, and add a
flags->string serializer, but that would require some effort and
possibly an ABI break), and that would require more parsing on the
scripting side (as you need to split the flags in the various
components).

An intermediary solution could consist in a manual flags->int
conversion, then we may add options support to AVStream and a generic
av_opt_get_flags_string(), and rely on that when we will bump major.

What do people think?
-- 
FFmpeg = Formidable and Fundamentalist Moronic Pacific Extensive Glue