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• Convert MP3 bitrate from a stream into another stream with ffmpeg

  10 juillet 2013, par Léon Pelletier

  Using ffmpeg, I would like to know if it's possible to convert mp3 bitrate as data chunks are received ?

  That means I would send slowly chunks to ffmpeg so that it outputs a mp3 with another bitrate.

  So in very-pseudo-code, it looks like it :

  1. MP3 Request from user

  2. Send the default mp3 to ffmpeg with parameters to convert to the desired bitrate.

  3. As it's writing a new file, write what as been writen so far in the Response outputstream (I'm in ASP.Net)

  Is that feasable or I need to switch to another technology ?

  [EDIT]

  For now, I'm trying a solution like this : Convert wma stream to mp3 stream with C# and ffmpeg

  [EDIT 2]

  I answered my question, and it is feasible with an url as input and standard output as output. Using an url allows to process a file chunk by chunk, and using stdout, we can access data while it is processed.

• ffmpeg : Perform filter at only 1 audio stream, recoding other stream

  7 mars 2023, par lhksoft

  I've got a mp4 video file with 2 audio streams. Both at e-ac3. I want the first stream recode to ac3, the other to aac. If I perform a filter for the 2nd stream, it seems ffmpeg performs it at both streams, but the first stream should be left alone - only recoded to ac3

  


  I use following in a cmd file to batch it at my videos :

  


  set tstLen=
rem set tstLen=-to 180

set audParam=-ac 2 -af "aresample=matrix_encoding=dplii,loudnorm=I=-16:LRA=11:TP=-1.5" -ar 48000 -c:a libfdk_aac -b:a 192k
%pathToFFMPeG% -hide_banner -y %tstLen% -i %1 -map 0:a:1 %audParam% "Y:\_\ToDo\%~n1.m4a"

set audParam=-c:a:0 ac3 -b:a:0 448k -c:a:1 copy
set audDefault=-disposition:a:0 default -disposition:a:1 none
%pathToFFMPeG% -hide_banner -y %tstLen% -i %1 -i "Y:\_\ToDo\%~n1.m4a" -map 0:v -map 0:a:0 -map 1 -c:v copy %audParam% %audDefault% "Y:\_\ToDo\%~nx1"


  


  Currently I need to create a m4a file containing only the stream I want it to be in aac, afterwards I encode the mp4 where the 1st stream is encoded to ac3 and injecting the m4a into it. The filter also will do a normalisation of the audio, and I don't want it to perform at the 1st audio stream.

  


  Is there a way to perform these tasks in 1 command, so I don't have to first create a m4a ?

  


  I tried with following code :

  


  set tstLen=
rem set tstLen=-to 180

set audParam=-c:a:0 ac3 -b:a:0 448k -ac:a:1 2 -af:a:1 "aresample=matrix_encoding=dplii,loudnorm=I=-16:LRA=11:TP=-1.5" -ar:a:1 48000 -c:a:1 libfdk_aac -b:a:1 192k
set audDefault=-disposition:a:0 default -disposition:a:1 none
%pathToFFMPeG% -hide_banner -y %tstLen% -i %1 -map 0 -c:v copy %audParam% %audDefault% "Y:\_\ToDo\%~nx1"


  


  But with this code also the first stream gets normalised and even the "dolby pro logic II" resample filter will be performed at the 1st stream, which it should't.

  


  NB : the %tstLen% code is for making a test of about 3 minutes to see if the result is what I wants it to be, while performing the filter in the 1st task can take some time.

  


• Convert MJPEG RTP stream to MP4 RTP stream with FFMPEG - how ?

  2 février 2019, par Shivan

  I’m already searching for a solution for several days how to convert an MJPEG rtp stream to MP4 rtp stream.

  Already tried something like this :

  ffmpeg -i rtsp://192.168.10.8:554/stream1/mobotix.mjpeg -rtsp_transport tcp -f H264 udp://192.168.10.5:8554

  ffmpeg then shows me like it’s doing something...

  frame=  612 fps= 11 q=25.0 size=    3243kB time=00:00:56.00 bitrate= 474.4kbits/s dup=275 drop=0 speed=0.981x

  Then I tried with VLC to open udp ://192.168.10.5:8554
  but it opens nothing simply the bar is running left/right forever.

  Do I need something like Simple RTP-Server (https://github.com/ossrs/srs) and then stream to that ?

  Best would be, when ffmpeg could host rtp itself...