but if we DID NOT add qscale, we can get one picture after sending one frame the the encoder at the same time; even if the src file having B frames
Carl Eugen Hoyos <[email protected]> 于2020年3月17日周二 下午11:13写道： > Am Di., 17. März 2020 um 16:04 Uhr schrieb penguin flying > <[email protected]>: > > > > using this cmd > > ffmpeg -i in.mp4 -copyts -f image2 -vframes 5 -y %03d.jpg > > will decode one frame and then encode it to one jpg at the same time, > > AND the picture will be encoded in default quality. > > > > BUT when I want to improve the quality of the image after adding the > param > > "qscale", > > ffmpeg -i in.mp4 -copyts -f image2 -vframes 5 -qscale:v 2 -y %03d.jpg > > > > I found that three or more frames must be send to the encoder before the > > first jpg comes out. > > > > How to send one frame and then one picture out when using "qscale" > > The output option -threads 1 should ensure this... > > > PS: the source file in.mp4 has B frames > > ... but this may not be possible for streams with B frames. > > Carl Eugen > _______________________________________________ > ffmpeg-user mailing list > [email protected] > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > [email protected] with subject "unsubscribe". _______________________________________________ ffmpeg-user mailing list [email protected] https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
