Audio processing. Is it possible to directly access the decoded audio data going into the analog input of a...












2












$begingroup$


When a computer transcodes an audio file from one file format to another, does the computer first decode it into the raw digital stream (exactly what is fed into the DAC for the audio output) , or does it do something different without having to completely decode it?



Take Spotify files for example, I believe that they are not in a standard MP3 format that can be played on any device. However, shouldn't it be relatively easy to convert these files into standard MP3 files, by first decoding them and then re-encoding to MP3 format?



Or would it require getting the analogue audio, converting it back to digital and then encoding again. My main query is, do we generally have access to this raw decoded digital audio data?










share|improve this question









$endgroup$

















    2












    $begingroup$


    When a computer transcodes an audio file from one file format to another, does the computer first decode it into the raw digital stream (exactly what is fed into the DAC for the audio output) , or does it do something different without having to completely decode it?



    Take Spotify files for example, I believe that they are not in a standard MP3 format that can be played on any device. However, shouldn't it be relatively easy to convert these files into standard MP3 files, by first decoding them and then re-encoding to MP3 format?



    Or would it require getting the analogue audio, converting it back to digital and then encoding again. My main query is, do we generally have access to this raw decoded digital audio data?










    share|improve this question









    $endgroup$















      2












      2








      2





      $begingroup$


      When a computer transcodes an audio file from one file format to another, does the computer first decode it into the raw digital stream (exactly what is fed into the DAC for the audio output) , or does it do something different without having to completely decode it?



      Take Spotify files for example, I believe that they are not in a standard MP3 format that can be played on any device. However, shouldn't it be relatively easy to convert these files into standard MP3 files, by first decoding them and then re-encoding to MP3 format?



      Or would it require getting the analogue audio, converting it back to digital and then encoding again. My main query is, do we generally have access to this raw decoded digital audio data?










      share|improve this question









      $endgroup$




      When a computer transcodes an audio file from one file format to another, does the computer first decode it into the raw digital stream (exactly what is fed into the DAC for the audio output) , or does it do something different without having to completely decode it?



      Take Spotify files for example, I believe that they are not in a standard MP3 format that can be played on any device. However, shouldn't it be relatively easy to convert these files into standard MP3 files, by first decoding them and then re-encoding to MP3 format?



      Or would it require getting the analogue audio, converting it back to digital and then encoding again. My main query is, do we generally have access to this raw decoded digital audio data?







      audio sound mp3 digital-to-analog






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 4 hours ago









      Engineer999Engineer999

      1211




      1211






















          2 Answers
          2






          active

          oldest

          votes


















          2












          $begingroup$

          A program to convert an .mp3 audio file-format into , say, an .ra (real audio) audio file-format needs fully to decode the mp3 file into raw waveform audio and then re-encode it into its new format.



          This raw audio waveform data can be contained within 32/64-bit floating point or some integer formats though. But when it's sent to audio DAC, it should be in an integer format; this depends on the PC audio standard and as far as I know, Windows (and like) systems use 8/16 bit integer formats at this stage (you have to check for their developer knowledge base for their latest implementations)



          So there can be a very slight difference between the raw data at the input buffer of DAC and raw data that reside in the system RAM, but they are both raw waveform data.



          Nevertheless, unless the the two audio formats have some common design layering, then it's not possible to transcode from one format to the other without full decoding of the original.



          Finally, analog audio is practically never required as it would introduce more errors and complexities than do anything useful.






          share|improve this answer









          $endgroup$





















            1












            $begingroup$

            You can transcode by going from any encoded format to a PCM format (which is the raw waveform as it would be sent to a DAC) and then re-encode in the new format. PCM is always the input to an encoder and the output of a decoder.



            Most perceptual codecs like MP3, AAC, or Vorbis (which Spotify uses) are all sub-band codecs and in theory it would be possible to transcode in the sub-band domain. However, the devil is in the details and it's really not worth the extra effort, especially since decode/encode is fast and super simple.



            Things can be more complicated if digital rights management or other copyright protection features are in place. In this case it may not be possible (or legal) to keep significant chunks of PCM format around.






            share|improve this answer











            $endgroup$













              Your Answer





              StackExchange.ifUsing("editor", function () {
              return StackExchange.using("mathjaxEditing", function () {
              StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
              StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
              });
              });
              }, "mathjax-editing");

              StackExchange.ready(function() {
              var channelOptions = {
              tags: "".split(" "),
              id: "295"
              };
              initTagRenderer("".split(" "), "".split(" "), channelOptions);

              StackExchange.using("externalEditor", function() {
              // Have to fire editor after snippets, if snippets enabled
              if (StackExchange.settings.snippets.snippetsEnabled) {
              StackExchange.using("snippets", function() {
              createEditor();
              });
              }
              else {
              createEditor();
              }
              });

              function createEditor() {
              StackExchange.prepareEditor({
              heartbeatType: 'answer',
              autoActivateHeartbeat: false,
              convertImagesToLinks: false,
              noModals: true,
              showLowRepImageUploadWarning: true,
              reputationToPostImages: null,
              bindNavPrevention: true,
              postfix: "",
              imageUploader: {
              brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
              contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
              allowUrls: true
              },
              noCode: true, onDemand: true,
              discardSelector: ".discard-answer"
              ,immediatelyShowMarkdownHelp:true
              });


              }
              });














              draft saved

              draft discarded


















              StackExchange.ready(
              function () {
              StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fdsp.stackexchange.com%2fquestions%2f56023%2faudio-processing-is-it-possible-to-directly-access-the-decoded-audio-data-going%23new-answer', 'question_page');
              }
              );

              Post as a guest















              Required, but never shown

























              2 Answers
              2






              active

              oldest

              votes








              2 Answers
              2






              active

              oldest

              votes









              active

              oldest

              votes






              active

              oldest

              votes









              2












              $begingroup$

              A program to convert an .mp3 audio file-format into , say, an .ra (real audio) audio file-format needs fully to decode the mp3 file into raw waveform audio and then re-encode it into its new format.



              This raw audio waveform data can be contained within 32/64-bit floating point or some integer formats though. But when it's sent to audio DAC, it should be in an integer format; this depends on the PC audio standard and as far as I know, Windows (and like) systems use 8/16 bit integer formats at this stage (you have to check for their developer knowledge base for their latest implementations)



              So there can be a very slight difference between the raw data at the input buffer of DAC and raw data that reside in the system RAM, but they are both raw waveform data.



              Nevertheless, unless the the two audio formats have some common design layering, then it's not possible to transcode from one format to the other without full decoding of the original.



              Finally, analog audio is practically never required as it would introduce more errors and complexities than do anything useful.






              share|improve this answer









              $endgroup$


















                2












                $begingroup$

                A program to convert an .mp3 audio file-format into , say, an .ra (real audio) audio file-format needs fully to decode the mp3 file into raw waveform audio and then re-encode it into its new format.



                This raw audio waveform data can be contained within 32/64-bit floating point or some integer formats though. But when it's sent to audio DAC, it should be in an integer format; this depends on the PC audio standard and as far as I know, Windows (and like) systems use 8/16 bit integer formats at this stage (you have to check for their developer knowledge base for their latest implementations)



                So there can be a very slight difference between the raw data at the input buffer of DAC and raw data that reside in the system RAM, but they are both raw waveform data.



                Nevertheless, unless the the two audio formats have some common design layering, then it's not possible to transcode from one format to the other without full decoding of the original.



                Finally, analog audio is practically never required as it would introduce more errors and complexities than do anything useful.






                share|improve this answer









                $endgroup$
















                  2












                  2








                  2





                  $begingroup$

                  A program to convert an .mp3 audio file-format into , say, an .ra (real audio) audio file-format needs fully to decode the mp3 file into raw waveform audio and then re-encode it into its new format.



                  This raw audio waveform data can be contained within 32/64-bit floating point or some integer formats though. But when it's sent to audio DAC, it should be in an integer format; this depends on the PC audio standard and as far as I know, Windows (and like) systems use 8/16 bit integer formats at this stage (you have to check for their developer knowledge base for their latest implementations)



                  So there can be a very slight difference between the raw data at the input buffer of DAC and raw data that reside in the system RAM, but they are both raw waveform data.



                  Nevertheless, unless the the two audio formats have some common design layering, then it's not possible to transcode from one format to the other without full decoding of the original.



                  Finally, analog audio is practically never required as it would introduce more errors and complexities than do anything useful.






                  share|improve this answer









                  $endgroup$



                  A program to convert an .mp3 audio file-format into , say, an .ra (real audio) audio file-format needs fully to decode the mp3 file into raw waveform audio and then re-encode it into its new format.



                  This raw audio waveform data can be contained within 32/64-bit floating point or some integer formats though. But when it's sent to audio DAC, it should be in an integer format; this depends on the PC audio standard and as far as I know, Windows (and like) systems use 8/16 bit integer formats at this stage (you have to check for their developer knowledge base for their latest implementations)



                  So there can be a very slight difference between the raw data at the input buffer of DAC and raw data that reside in the system RAM, but they are both raw waveform data.



                  Nevertheless, unless the the two audio formats have some common design layering, then it's not possible to transcode from one format to the other without full decoding of the original.



                  Finally, analog audio is practically never required as it would introduce more errors and complexities than do anything useful.







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered 3 hours ago









                  Fat32Fat32

                  15.6k31232




                  15.6k31232























                      1












                      $begingroup$

                      You can transcode by going from any encoded format to a PCM format (which is the raw waveform as it would be sent to a DAC) and then re-encode in the new format. PCM is always the input to an encoder and the output of a decoder.



                      Most perceptual codecs like MP3, AAC, or Vorbis (which Spotify uses) are all sub-band codecs and in theory it would be possible to transcode in the sub-band domain. However, the devil is in the details and it's really not worth the extra effort, especially since decode/encode is fast and super simple.



                      Things can be more complicated if digital rights management or other copyright protection features are in place. In this case it may not be possible (or legal) to keep significant chunks of PCM format around.






                      share|improve this answer











                      $endgroup$


















                        1












                        $begingroup$

                        You can transcode by going from any encoded format to a PCM format (which is the raw waveform as it would be sent to a DAC) and then re-encode in the new format. PCM is always the input to an encoder and the output of a decoder.



                        Most perceptual codecs like MP3, AAC, or Vorbis (which Spotify uses) are all sub-band codecs and in theory it would be possible to transcode in the sub-band domain. However, the devil is in the details and it's really not worth the extra effort, especially since decode/encode is fast and super simple.



                        Things can be more complicated if digital rights management or other copyright protection features are in place. In this case it may not be possible (or legal) to keep significant chunks of PCM format around.






                        share|improve this answer











                        $endgroup$
















                          1












                          1








                          1





                          $begingroup$

                          You can transcode by going from any encoded format to a PCM format (which is the raw waveform as it would be sent to a DAC) and then re-encode in the new format. PCM is always the input to an encoder and the output of a decoder.



                          Most perceptual codecs like MP3, AAC, or Vorbis (which Spotify uses) are all sub-band codecs and in theory it would be possible to transcode in the sub-band domain. However, the devil is in the details and it's really not worth the extra effort, especially since decode/encode is fast and super simple.



                          Things can be more complicated if digital rights management or other copyright protection features are in place. In this case it may not be possible (or legal) to keep significant chunks of PCM format around.






                          share|improve this answer











                          $endgroup$



                          You can transcode by going from any encoded format to a PCM format (which is the raw waveform as it would be sent to a DAC) and then re-encode in the new format. PCM is always the input to an encoder and the output of a decoder.



                          Most perceptual codecs like MP3, AAC, or Vorbis (which Spotify uses) are all sub-band codecs and in theory it would be possible to transcode in the sub-band domain. However, the devil is in the details and it's really not worth the extra effort, especially since decode/encode is fast and super simple.



                          Things can be more complicated if digital rights management or other copyright protection features are in place. In this case it may not be possible (or legal) to keep significant chunks of PCM format around.







                          share|improve this answer














                          share|improve this answer



                          share|improve this answer








                          edited 54 mins ago









                          Community

                          1




                          1










                          answered 2 hours ago









                          HilmarHilmar

                          10.2k1218




                          10.2k1218






























                              draft saved

                              draft discarded




















































                              Thanks for contributing an answer to Signal Processing Stack Exchange!


                              • Please be sure to answer the question. Provide details and share your research!

                              But avoid



                              • Asking for help, clarification, or responding to other answers.

                              • Making statements based on opinion; back them up with references or personal experience.


                              Use MathJax to format equations. MathJax reference.


                              To learn more, see our tips on writing great answers.




                              draft saved


                              draft discarded














                              StackExchange.ready(
                              function () {
                              StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fdsp.stackexchange.com%2fquestions%2f56023%2faudio-processing-is-it-possible-to-directly-access-the-decoded-audio-data-going%23new-answer', 'question_page');
                              }
                              );

                              Post as a guest















                              Required, but never shown





















































                              Required, but never shown














                              Required, but never shown












                              Required, but never shown







                              Required, but never shown

































                              Required, but never shown














                              Required, but never shown












                              Required, but never shown







                              Required, but never shown







                              Popular posts from this blog

                              How to label and detect the document text images

                              Vallis Paradisi

                              Tabula Rosettana