[FFmpeg-user] (de)-interlacing question

Andy Furniss adf.lists at gmail.com
Thu Nov 24 14:36:52 EET 2016


Toerless Eckert wrote:
> On Wed, Nov 23, 2016 at 11:30:55AM +0100, Moritz Barsnick wrote:
>>> the mediaportal H264 mp4 file is 720p50 but actually 720p25 with
>>> duplicated frames,
>>
>> I never noticed that. :-/ (Why would they duplicate them?) I don't have
>> any "true 50 fps" show to check right now. A random ARD Mediathek
>> archive file (yesterday's Tagesschau) shows this:
>
> Well, i'd assume they reduce the effective framerate to 25 to get lower
> bitrate, and they duplicate to get better player compatibility ?
>
>> Input #0, hls,applehttp, from 'http://hls.tagesschau.de/i/video/2016/1122/TV-20161122-2026-4701.,webs,websm,webm,webml,webl,webxl,.h264.mp4.csmil/index_5_av.m3u8':
>
> ... Which program do you use for this output ?
>
> I downloaded with MediathekView, so i got non-hls.
>
> Also shows probably the same with ffprobe:
>
> Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'zdf.mp4':
>    Metadata:
>      major_brand     : mp42
>      minor_version   : 0
>      compatible_brands: isom
>      creation_time   : 2016-11-15 09:18:01
>    Duration: 00:28:30.04, start: 0.000000, bitrate: 3776 kb/s
>      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720 [SAR 1:1 DAR 16:9], 3582 kb/s, 50 fps, 50 tbr, 50k tbn, 100 tbc (default)
>      Metadata:
>        creation_time   : 2016-11-15 09:18:01
>        handler_name    : MP4 Video Media Handler
>        encoder         : AVC Coding
>      Stream #0:1(deu): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 189 kb/s (default)
>      Metadata:
>        ...
>
> Aka: Don't see anything that would indicate frame duplication, so
> all i can do is trust the step by step playback from vlc or mplayer.

I can't reproduce getting ffmpeg to call 50fps or mplayer/vlc to dup on 
framestep, though as I said mplayer gets confused.

Maybe there is something in the raw chunks that makes MediathekView see 
50 when it makes the mp4.

As the above link is not live you can just download the m3u8 with wget, 
look at it and wget a chunk from one of the links it contains.

ffmpeg does not call 50 fps if I do that.




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