The 2025-05-22T14:33:22.000+02:00, Ramiro Polla <ramiro.po...@gmail.com> wrote :
> Hi, > > On Thu, May 22, 2025 at 1:59 PM Ronald S. Bultje <rsbul...@gmail.com> wrote: > >> On Wed, May 21, 2025 at 9:34 AM Timothée < >> timothee.informati...@regaud-chapuy.fr> wrote: >> >>> I am interested in expanding ffmpeg's capabilities to extract >>> low-level data from video codecs. Specifically, I'd like to >>> implement functionality that would allow exporting frame data, >>> macroblock information, quantization tables, and similar >>> codec-specific elements to binary files for further analysis. >>> After searching through the documentation and existing features, >>> I haven't found similar functionality, though I may have missed >>> something. Has this been implemented before, or are there >>> related features I should examine? >> >> Some older codecs implement minor variants for this, e.g. grep >> for AV_FRAME_DATA_MOTION_VECTORS, which attaches a frame's motion >> vectors to the picture data. I believe there's an example app and >> possibly a filter to overlay MVs on top of the video frame based >> on this concept. You could extend this to cover other (macro)block >> info. There used to be a variant of this for quant-tables also but >> I can't find it, maybe it was removed. > > If I recall correctly, we wanted to move away from exporting more > of this kind of codec-specific information as picture data. > Timothée, this kind of feature depends a lot on the codec that you > want to work with. It will also depend on which syntax elements you > need from the codec. In FFmpeg, there is the CBS code which > describes the bitstream for a few codecs, which might help you. I > have a separate project (called FFglitch), which lets you export > some elements (such as quantization tables, dct coefficients, and > motion vectors) from some codecs (jpeg, mpeg2, mpeg4) to JSON > format, and even modify them in the bitstream. In the end, it will > depend on what you want to do with the extracted low-level data, and > for which codecs. Ramiro Thank you for your response and for mentioning FFglitch - it looks like an excellent project that's very relevant to what I'm trying to accomplish. I have a question about FFglitch's capabilities: is it possible to extract quantization parameter (QP) tables using ffedit? I've reviewed the documentation but may have missed this functionality if it exists. Ideally I would want to extract data for all existing codecs, but I know this is impossible. My current focus is on implementing this feature for H.264, with plans to extend support to H.265 and AVI formats as well. I want to extract this data for scientific use. Thank you again for your time and suggestions. Timothée _______________________________________________ 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".
