[MPlayer-dev-eng] patch for PNG output

[Reimar Döffinger]

Hello,
On Tue, Oct 02, 2007 at 11:32:34AM -0400, Vincent Chapdelaine-Couture wrote:
> We propose a simple change to the PNG output module to create
> concatenated PNG data in a single file instead of multiple files.
>
> Currently, there is no way to extract a stream of "lossless high
> quality" images from mplayer without saving the images to disk. All the 
> output modules generating images are either lossy (jpeg, gif89a) or saved 
> in single files (png, pnm, tga). Having a stream of PNG is ideal for 
> automatic processing of the images.

Why not mencoder -ovc lavc -lavcopts vcodec=png -of rawvideo ?


> @@ -34,6 +34,8 @@
>  
>  int z_compression = Z_NO_COMPRESSION;
>  static int framenum = 0;
> +char *single_file_name=NULL; // if not null, then output there
> +FILE *single_file=NULL;	// NULL -> regulier. Not null: send all images there

Must be static, and comments should be doxygen-compatible. And regulier
may be French but certainly not English.

> @@ -97,12 +99,16 @@
>          return png;
>      }
>      
> -    png.fp = fopen (fname, "wb");
> -    if (png.fp == NULL) {
> - 	mp_msg(MSGT_VO,MSGL_WARN, MSGTR_LIBVO_PNG_ErrorOpeningForWriting, strerror(errno));
> -       	png.status = ERROR;
> -       	return png;
> -    }	    
> +    if( single_file ) {
> +	    png.fp = single_file;
> +    }else{
> +	    png.fp = fopen (fname, "wb");
> +	    if (png.fp == NULL) {
> +		mp_msg(MSGT_VO,MSGL_WARN, MSGTR_LIBVO_PNG_ErrorOpeningForWriting, strerror(errno));
> +		png.status = ERROR;
> +		return png;
> +	    }	    
> +    }

Cosmetics. Indentation must be changed in a separate patch.
And I don't think it would hurt just to do
png.fp = single_file ? single_file : fopen (fname, "wb");

> @@ -219,8 +232,19 @@
>      return 1;
>  }
>  
> +static int test_single_file_name(const char **name) {
> +	single_file=fopen(*name,"wb");
> +	if( single_file==NULL ) {
> +		fprintf(stderr,"UNABLE TO OPEN %s for writing\n",*name);
> +        	return 0; // not supported
> +	}
> +	return 1;
> +}
> +
> +
>  static opt_t subopts[] = {
>      {"z",   OPT_ARG_INT, &z_compression, (opt_test_f)int_zero_to_nine},
> +    {"single",   OPT_ARG_MSTRZ, &single_file_name, (opt_test_f)test_single_file_name},

Wrong, test functions must be idempotent, they may be called more than
once (esp. since -vo png:single=a:single=b:single=c is valid even though
it is rather pointless to specify it more than once).

Greetings,
Reimar Döffinger