Quoting Eran Kornblau (2020-03-03 10:48:31) > > > > > > -----Original Message----- > > From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of Hendrik > > Leppkes > > Sent: Tuesday, March 3, 2020 11:08 AM > > To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org> > > Subject: Re: [FFmpeg-devel] Calculating audio frame rate > > > > On Tue, Mar 3, 2020 at 8:22 AM Eran Kornblau <eran.kornb...@kaltura.com> > > wrote: > > > > > > Hi all, > > > > > > First, I apologize for asking a question not directly related to ffmpeg > > > development, but hope you can still help me... > > > > > > I'm looking for some code to calculate the frame rate of audio, based > > > on parameters such as the codec id, sampling rate, channels, codec > > > private data etc. > > > For example, if the codec is AAC and the sampling rate is 44.1KHz, the > > > frame rate would be 44100/1024= ~43 fps (assuming each frame has 1024 > > > samples, not 960) > > > > > > Has anyone ever written/bumped into something that implements this across > > > multiple codecs? > > > > > > > The frame size of audio codecs is pretty much only dependent on the codec > > itself, which means you would need to basically hard-code this for every > > codec you care about. > > Ultimately I wonder however, when does this information really matter? > > Thanks Hendrik. > > What I'm trying to do is to estimate the final bitrate of the stream, that > includes the muxing overhead. > I'm generating an HLS stream, and would like to output the right 'bandwidth' > attribute for the master m3u8. > For example, when using MPEG-TS container I may need to add up to 10% to the > original bitrate, in order to get > the 'real' bitrate of the segments, when using fMP4 it's much less. > > I don't have the audio/video frames at hand, and would like to calculate this > estimate based on the media info. > For example, with video, I'm assuming on average a padding of 1/2 MPEG-TS > packet per frame, to that I'm adding > the size of the PES header and multiplying everything by 188/184 to account > for the MPEG-TS header. > So, I wrote some formula that depends on - net bitrate, frame rate and > segment duration. > The audio frame rate probably has a tiny effect here, but if there is an easy > solution for it, I rather add it. >
There is av_get_audio_frame_duration[2]() in libavcodec, but it only handles some codecs. Not AAC for example, probably because it can have a bunch of different frame sizes depending on bitstream parameters. -- Anton Khirnov _______________________________________________ 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".
