On July 29, 2020 3:13:34 PM GMT+08:00, Jaeho Bang <jaeho.b...@gmail.com> wrote: >Dear Paul, >Thank you for the reply! I must have done a bad job explaining, sorry >about >that. There is some underlying information that I have left out. My >initial >clustering algorithm / representative frame selection algorithm >actually >spits out a frame importance hierarchy. I want to implement a custom >decoder because it needs to process inputs such as 'select 100 most >important frames of this video'. Rather than decoding the entire video >and >choosing the 100 most important frames based on frame importance >hierarchy, >I want to only decode the frames that I specify (By having a custom >encoder, I have already forced these frames to be i-frames, hence >minimum >computation is required). The goal of this decoder is to minimize >memory >footprint (since decoding entire video into image frames increases >memory >usage by 100x according to my experiments) while maximizing decoding >speed. >Does this provide a clearer reason why I am thinking of implementing a >custom decoder? Please feel free to ask for clarifications. >
You can add custom info to container or out-of-band to help select which packet to decoding. The custom info doesn't belong to the codec normally. >Thank you, >Jaeho Bang > >On Wed, Jul 29, 2020 at 3:31 PM Paul B Mahol <one...@gmail.com> wrote: > >> On 7/29/20, Jaeho Bang <jaeho.b...@gmail.com> wrote: >> > Dear members of ffmpeg-devel, >> > >> > I am currently working on a research project and from looking over >the >> > examples and documentation in the ffmpeg repository, I believe I >need to >> > implement a custom encoder / decoder to perform my task. >> > >> > To first explain the project idea, currently I am working mainly >with >> > surveillance footages. Using a traditional video decoder, I convert >the >> > video into series of image frames and perform clustering to create >frame >> > groups. Then using some performance metric, my algorithm selects a >> > representative frame from each group. By implementing a custom >encoder >> and >> > decoder, I aim to improve the speed of extracting these >representative >> > frames. >> > >> > To further explain, I would like the custom encoder to be able to >force >> the >> > frames I have chosen (representative frames) to be i-frames. The >> assumption >> > is that when analyzing videos, we only need to evaluate these >> > representative frames instead of the whole video (this I have >already >> > experimentally confirmed), and extracting i-frames is faster than >> > extracting a combination of i-frames, b-frames, and p-frames. >> > >> > Also, I would like to implement a decoder to quickly extract the >series >> of >> > frames I give as input (they will all be i-frames). Through >preliminary >> > experiments, I realized that extracting only i-frames by using the >> command >> > 'select pict_type\I' query command only gives a 2x speed boost >compared >> to >> > extracting all frames within the video. Hopefully, by implementing >a >> custom >> > decoder, I aim to further increase this extraction speed. >> > >> > Is there any code I can refer to? Is my assumption of 'if I were to >> > implement a custom decoder, the extraction speed would be faster >than >> using >> > the keyword select to get all the i frames' valid? >> > >> > Any help would be greatly appreciated. Thank you and have a >wonderful >> day. >> > >> >> Sorry, but with all due respect, the need for custom decoder does not >> make any sense. >> >> > Sincerely, >> > Jaeho Bang >> > >> > -- >> > *Jaeho Bang* >> > *PhD Student in Computer Science* >> > Georgia Institute of Technology >> > North Ave NW, Atlanta, GA 30332, USA >> > _______________________________________________ >> > ffmpeg-devel mailing list >> > ffmpeg-devel@ffmpeg.org >> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> > >> > To unsubscribe, visit link above, or email >> > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". >> _______________________________________________ >> ffmpeg-devel mailing list >> ffmpeg-devel@ffmpeg.org >> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> >> To unsubscribe, visit link above, or email >> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". > > > >-- >*Jaeho Bang* >*PhD Student in Robotics* >Georgia Institute of Technology >North Ave NW, Atlanta, GA 30332, USA >_______________________________________________ >ffmpeg-devel mailing list >ffmpeg-devel@ffmpeg.org >https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > >To unsubscribe, visit link above, or email >ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". -- 使用 K-9 Mail 发送自我的Android设备。 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
