вс, 1 янв. 2023 г., 09:10 Terry Corbet <[email protected]>:
> I have recently discovered how to use the Audacity Envelope Tool to turn > a standard stereo MP3 file into a modified one in which throughout the > entire duration of the clip the apparent source of the sounds will > traverse from left to right. may be pan filter can do something by altering volumes of individual channels but as far as I can see you can't change its parameters at runtime? https://ffmpeg.org/ffmpeg-filters.html#Changing-options-at-runtime-with-a-command ==== Filter pan Remix channels with coefficients (panning). Inputs: #0: default (audio) Outputs: #0: default (audio) pan AVOptions: args <string> ..F.A...... === no T , as you can see (ffmpeg 5.1) I wonder if our software (cinelerra-gg, video editor, so a bit heavyweight) can do this via built-in keyframing .. I'll ask on our maillist. While I could use that workflow to > manually perform the same transformation on multiple files, for my own > use as well as to help other family members [who generally have limited > computer skills] I want to automate that workflow. > > Over the past four days I have played as much catch-up on the many > topics and toolkits which appear might permit me to engineer a software > solution to this requirement. As a newbie, I probably will not > correctly summarize what I believe to be the possible tools and > approaches, so please forgive any misuse to the correct terminology. I > hope/believe that I might be able to state my concepts/questions in a > manner which will be most considerate of the time of those who > participate in this mailing list and most quickly help me move closer to > a good approach to the challenge. > > 01. I have managed to download the libraries which are used for the > maintenance of the ffmpeg, ffprobe and ffplay triumvirate of tools. > > 02. I have managed to successfully build some sample C programs [taken > from the doc\examples sub-directory and other miscellaneous snippets > found by following the wonderful links from your Wiki] using the > CodeBlocks IDE framework. > > 03. I have squirreled my way through the parts of the Doxygen > documentation which seem like they would be most apropos. > > What I did not discover was any functions or examples of what I assumed > I would be needing to do, which essential would be to process the audio > frames of the FrontLeft [FL] and FrontRight [FR] channels of coming out > of a stream of packets. That caused me to think that perhaps I would > find examples of that processing by searching the Audacity sources to > learn when and how they use the ffmpeg libraries. And somewhere between > the Audacity and FFmpeg sites I stumbled upon some sources and some > documentation concerning what I suppose are two reasonable libraries > devoted to "resampling" -- soxr and swr. > > It was about at that point that I concluded that my modification of the > sampled frames probably does not fall within the ambit of what is meant > by resampling at all and that led to an investigation of what Nyquist > was all about. Wow, what a guy Mr. Dannenberg must be. The 2007 > Nyquist Reference Manual is a jaw-dropping read. > > I think that is enough background/context. Here's were I would > appreciate any suggestions: > > A. Would it be possible to accomplish the steps necessary to achieve > the desired result just using ffmpeg.exe? I imagine that, using the > command line tool and an appropriate shell scripting language, it might > be necessary to make multiple passes of the original .mp3 file and/or > the two separate channels. I am not concerned about that loss of > throughput; it will always be far faster than any manual procedure. > > B. Nonetheless, there are some advantages that would accrue from > accomplishing the work entirely in an application .exe with a little GUI > glitter to help the user be able to attempt some trial-and-error > [preview] with slight changes in some of the parameters of the task > depending upon the nature of the audio content and the manner in which > the user will eventually play the output on different devices in > different environments. Since I will not have the capabilities for > building an Envelope in the manner that Nyquist [Lisp] accomplishes > that, can anyone point me to any sample code doing that in C with the > eight ffmpeg .dll libraries? > > C. Or -- and I appreciate that it is not fair to ask this of this mail > group -- but I would appreciate any experience/advice as to whether the > solution really ought to be accomplished by some scripting and/or macro > facilities wrapped around Audacity? > > Thank you so much for the fantastic capabilities you have provided with > the entire FFmpeg effort and for your patience in reading through my > questions as the bell is about to strike on the New Year. > > _______________________________________________ > Libav-user mailing list > [email protected] > https://ffmpeg.org/mailman/listinfo/libav-user > > To unsubscribe, visit link above, or email > [email protected] with subject "unsubscribe". >
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