[FFmpeg-devel] regression - mpeg2 interlace/topfield flags not set anymore

christophelorenz christophelorenz
Sat Jan 26 00:57:15 CET 2008

Michael Niedermayer wrote:

>On Thu, Jan 24, 2008 at 03:46:50PM +0100, christophelorenz wrote:
>>Seems something has changed between rev 10908 and current causing the 
>>interlaced and field order flag to be set to a wrong value.
>>ffmpeg -i "source.avi" -y -flags +ildct+ilme -bufsize 2000k -b 7600k 
>>-maxrate 8000k -top 1 -vcodec mpeg2video output.m2v
>bug not reproduceable tff/interlaced flags are correct 
>-> closed/invalid
I have been able to locate the problem and conditions more precisely :

All linux builds are ok, it only happens under win32.
It doesn't depend on the source material format.
It happens with my builds, and other win32 binaries found on the net.

After building a bunch or revisions, I found the problem appeared when 
moving to rev 11142.

The only affected file is ffmpeg.c from rev 11117 to 11142 done by 
michael  commented "Fix non-numeric AVOptions."

I took rev 11608 and reverted some code to locate the problem and found 
out that reverting the last change of ffmpeg.c fixes the problem.

on svn, last ffmpeg.c line 3278 :
    for(i=0; i<opt_name_count; i++){
        char buf[256];
        const AVOption *opt;
        const char *str= av_get_string(avformat_opts, opt_names[i], 
&opt, buf, sizeof(buf));
        if(str && (opt->flags & AV_OPT_FLAG_ENCODING_PARAM))
            av_set_string(oc, opt_names[i], str);

replaced by previous code : (from rev 11117)
    for(i=0; i<opt_name_count; i++){
        const AVOption *opt;
        double d = av_get_double(avformat_opts, opt_names[i], &opt);
        if(!isnan(d) && (opt->flags&AV_OPT_FLAG_ENCODING_PARAM))
            av_set_double(oc, opt_names[i], d);

Restore the correct operation on interlaced mpegs.

Obviously a simple arg parsing problem... but I must say I have no clue 
why current rev it doesn't work as expected, more specifically under 
I'll add some debug dump to see what happens, meanwhile if someone has 
an idea ;-)


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