2015-01-09 18:00 GMT+01:00 tim nicholson <[email protected]>:
> On 09/01/15 15:30, Valentin NOEL wrote: > > 2015-01-09 15:29 GMT+01:00 tim nicholson < > [email protected]>: > > > >> [...] > >> It means that I was making a pragmatic suggestion for something you > >> could try immediately to solve your issue, rather than trying to get > >> bogged down in technical details too early. > >> > > > > Actually, I need to add this flag "+cgop" because I need to generate > closed > > GOP. > > Other encoders allow finishing closed GOP with B-frames (with only > backward > > reference), so I wonder whether FFmpeg cannot allow doing this, or > whether > > I do not use it correctly. > > > > Well does toggling that option off change things at all? > (Notwithstanding that for real use you need it, just trying to see what > might affect the result as I know chaging this can affect the bframe > count). > Yes, it generates a first GOP of 10 frames : I B B P B B P B B P The following GOPs are containing 12 frames : B B I B B P B B P B B P Checking the gop headers in the bitstream, it appears that all the GOPs are open, even the first (I would think it is closed). > -b_strategy 0 is the default so that setting should be doing nothing, > have you experimented with different values? > -b_strategy 1 alone gives : I P P P P P P P P P P P P but it depends on the setting -b_sensitivity (I didn't find what the default value is) : - values from 1 to ~4 : some B-frames appear sometimes (decreasing with the option value) and variable GOP length - values from ~4 and more : I P P P P P P P P P P P -b_strategy 2, does not give better results but much longer process : I B P B B P B B P B B P Results are quiet the same without the +cgop flag. > > >>> Thanks. > >>> > >>>[....] > > > -- > Tim. > Key Fingerprint 38CF DB09 3ED0 F607 8B67 6CED 0C0B FC44 8B0B FC83 > _______________________________________________ > ffmpeg-user mailing list > [email protected] > http://ffmpeg.org/mailman/listinfo/ffmpeg-user > _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user
