aftering adding -threads 1 in the cmd, IT WORKS. thanks. penguin flying <[email protected]> 于2020年3月17日周二 下午11:25写道：
> 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".
