[FFmpeg-user] Framerate Question

[Jared McIntyre]

I guess it is possible, but there are subtle artifact differences between the frames if you look close enough (especially when they fade to and from commercial).

On Mar 4, 2012, at 9:06 PM, Dennis wrote:

> Its could be a decoder flag that signals to video renderer to play
> each frame twice, that's done after decoding of the frame is
> completed.
> 
> On 3/4/12, Jared McIntyre <jmcintyre at dfsoftware.com> wrote:
>> I'm re-encodeing broadcast video. The source was apparently 720 30fps, but
>> is being broadcast 60fps where every frame appears twice. I thought I'd try
>> to save some space by re-encoding and using 30fps to cut out every other
>> frame. I used the following command:
>> 
>> ffmpeg -i in.mpg -acodec libfaac -ab 160k -crf 23.1 -vcodec libx264 -tune
>> animation -preset faster -profile baseline -f mp4 -r 29.97 out.mp4
>> 
>> I was a bit surprised to find out that if I used -r 29.97 I would get a file
>> with half the frames, but a larger size than if I hadn't done so. I'm sure
>> I'm misunderstanding something, but is this the expected behavior? Here is
>> the log data in case about the encodeing:
>> 
>> Seems stream 0 codec frame rate differs from container frame rate: 119.88
>> (120000/1001) -> 59.96 (90000/1501)
>> Input #0, mpeg, from 'in.mpg':
>>  Duration: 00:02:30.91, start: 0.328367, bitrate: 11748 kb/s
>>    Stream #0.0[0x1e0]: Video: mpeg2video (Main), yuv420p, 1280x720 [PAR 1:1
>> DAR 16:9], 38810 kb/s, 59.96 fps, 59.96 tbr, 90k tbn, 119.88 tbc
>>    Stream #0.1[0x80]: Audio: ac3, 48000 Hz, 5.1, s16, 384 kb/s
>> [buffer @ 0x101a33900] w:1280 h:720 pixfmt:yuv420p tb:1/1000000 sar:1/1
>> sws_param:
>> [libx264 @ 0x10204a000] using SAR=1/1
>> [libx264 @ 0x10204a000] using cpu capabilities: MMX2 SSE2Fast SSSE3
>> FastShuffle SSE4.1 Cache64
>> [libx264 @ 0x10204a000] profile Constrained Baseline, level 3.1
>> [libx264 @ 0x10204a000] 264 - core 115 - H.264/MPEG-4 AVC codec - Copyleft
>> 2003-2011 - http://www.videolan.org/x264.html - options: cabac=0 ref=4
>> deblock=1:1:1 analyse=0x1:0x111 me=hex subme=4 psy=1 psy_rd=0.40:0.00
>> mixed_ref=0 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11
>> fast_pskip=1 chroma_qp_offset=0 threads=3 sliced_threads=0 nr=0 decimate=1
>> interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0
>> keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=20 rc=crf
>> mbtree=1 crf=23.1 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40
>> aq=1:0.60
>> Output #0, mp4, to 'out.mp4':
>>  Metadata:
>>    encoder         : Lavf52.110.0
>>    Stream #0.0: Video: libx264, yuv420p, 1280x720 [PAR 1:1 DAR 16:9],
>> q=2-31, 200 kb/s, 2997 tbn, 29.97 tbc
>>    Stream #0.1: Audio: libfaac, 48000 Hz, 5.1, s16, 160 kb/s
>> Stream mapping:
>>  Stream #0.0 -> #0.0
>>  Stream #0.1 -> #0.1
>> 
>> 
>> 
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