[FFmpeg-devel] [PATCH 3/3] lavf/gif: trim unecessary long netscape ext code.

[Paul B Mahol]

On 4/18/13, Clement Boesch <ubitux at gmail.com> wrote:
> Extension description comments are now placed along the avio calls, the
> always defined macro removed, and the always true loop_count check as
> well (loop option is bound to 0-65535).
> ---
>  libavformat/gif.c | 49 ++++++++++---------------------------------------
>  1 file changed, 10 insertions(+), 39 deletions(-)
>
> diff --git a/libavformat/gif.c b/libavformat/gif.c
> index 282fb55..30aa53b 100644
> --- a/libavformat/gif.c
> +++ b/libavformat/gif.c
> @@ -27,12 +27,6 @@
>  #include "libavutil/log.h"
>  #include "libavutil/opt.h"
>
> -/* slows down the decoding (and some browsers don't like it) */
> -/* update on the 'some browsers don't like it issue from above:
> - * this was probably due to missing 'Data Sub-block Terminator'
> - * (byte 19) in the app_header */
> -#define GIF_ADD_APP_HEADER // required to enable looping of animated gif
> -
>  static int gif_image_write_header(AVIOContext *pb, int width, int height,
>                                    int loop_count, uint32_t *palette)
>  {
> @@ -57,39 +51,16 @@ static int gif_image_write_header(AVIOContext *pb, int
> width, int height,
>          avio_w8(pb, 0); /* aspect ratio */
>      }
>
> -    /* update: this is the 'NETSCAPE EXTENSION' that allows for looped
> animated
> -     * GIF, see http://members.aol.com/royalef/gifabout.htm#net-extension
> -     *
> -     * byte   1       : 33 (hex 0x21) GIF Extension code
> -     * byte   2       : 255 (hex 0xFF) Application Extension Label
> -     * byte   3       : 11 (hex (0x0B) Length of Application Block
> -     *                          (eleven bytes of data to follow)
> -     * bytes  4 to 11 : "NETSCAPE"
> -     * bytes 12 to 14 : "2.0"
> -     * byte  15       : 3 (hex 0x03) Length of Data Sub-Block
> -     *                          (three bytes of data to follow)
> -     * byte  16       : 1 (hex 0x01)
> -     * bytes 17 to 18 : 0 to 65535, an unsigned integer in
> -     *                          lo-hi byte format. This indicate the
> -     *                          number of iterations the loop should
> -     *                          be executed.
> -     * bytes 19       : 0 (hex 0x00) a Data Sub-block Terminator
> -     */
> -
> -    /* application extension header */
> -#ifdef GIF_ADD_APP_HEADER
> -    if (loop_count >= 0 && loop_count <= 65535) {
> -        avio_w8(pb, 0x21);
> -        avio_w8(pb, 0xff);
> -        avio_w8(pb, 0x0b);
> -        // bytes 4 to 14
> -        avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
> -        avio_w8(pb, 0x03); // byte 15
> -        avio_w8(pb, 0x01); // byte 16
> -        avio_wl16(pb, (uint16_t)loop_count);
> -        avio_w8(pb, 0x00); // byte 19
> -    }
> -#endif
> +    /* "NETSCAPE EXTENSION" for looped animation GIF */
> +    avio_w8(pb, 0x21); /* GIF Extension code */
> +    avio_w8(pb, 0xff); /* Application Extension Label */
> +    avio_w8(pb, 0x0b); /* Length of Application Block */
> +    avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
> +    avio_w8(pb, 0x03); /* Length of Data Sub-Block */
> +    avio_w8(pb, 0x01);
> +    avio_wl16(pb, (uint16_t)loop_count);
> +    avio_w8(pb, 0x00); /* Data Sub-block Terminator */
> +
>      return 0;
>  }
>
> --
> 1.8.2.1
>
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>

lgtm