Re: [fpc-pascal] where to find materials about MP3 file format
Lets try to gues how MP3directcut work. The right is, that I can remove and move block of MP3 files when it is loaded. For example, I can copy part of MP3 audio data to clipboard and paste it to other part of loaded other MP3 file. And there is no long time while working by this way. So MR Pesh must use some very smart approach. When I choose save all function, data are stored to other file. Other temporary file is being created. Yes, volume function is being used also if user choose it. May be, that somebody have invented several complex mathematical formulas which can remove data of MP3 files without decompress it. Sure, some ststrange sound can happen, if user cut some part of active sound, but it is also possible when using audio editors which open MP3 file and decompress it. I must start from The most simple steps. How to detect key presses while using Android unit And PPCJVM ANdroid JVM target mode. To know, if user have pressed left arrow, right arrow on his external bluetooth keyboard. Next event will be based on GUI element presses detection by using onwievclick procedure. So condition blocks will assign two various events. From Bluetooth keyboard or other keyboard. The disadvantage of my desire is The fact, that I must always unhyde keyboard so other commands will detect keyboard presses, so keyboard will interfere with app GUI on The screen. But there is no other way. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] where to find materials about MP3 file format
El 15/08/2019 a las 11:04, George Bakhtadze escribió: mp3 is a loosy audio format. It means that some part of information is lost while encoding. So doing a decoding/encoding cycle just to remove some piece of file is a bad idea. I'd try to find a way to remove piece of audio data without decompressing the file similar to lossless operations on JPEG files. Hello, As JPEG only have limited operations without decompressing (limited rotation and limited cropping), mp3 also have limited operations without decompressing, in this case only frame volume change. -- ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] where to find materials about MP3 file format
Hello, 14.08.2019, 23:24, "Mgr. Janusz Chmiel" : > But how to achieve The complex algorithm for recreating MP3 file. It> will not be easy walk across The park. I will also have to use effective> approach to prevent memory allocation problems. mp3 is a loosy audio format. It means that some part of information is lost while encoding.So doing a decoding/encoding cycle just to remove some piece of file is a bad idea.I'd try to find a way to remove piece of audio data without decompressing the file similar to lossless operations on JPEG files. ---Best regards, George ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] where to find materials about MP3 file format
El 14/08/2019 a las 22:23, Mgr. Janusz Chmiel escribió: I have A very big and non easy dream. Making similar MP3 editor like MP3 direct cut for Windows is. But sure! [...] operations to assign beginning of block and its end. And mainly, I want to use remove block command, which will hae immediate effect. So MP3 [...] Who of us would have some tip how to find MP3 file format technical specifications? Hello, There are several documents about the MP3 format, but you only need for sure ID3V1, ID3V2 and MP3 frame format. You need ID3V1 and ID3V2 in order to skip this information (if you will not use it, as it is metadata only) and the MP3 frame format if you want to fast scan MP3 time duration and scan for stream errors. https://www.mp3-tech.org/programmer/frame_header.html All other operations should be done with decompressed audio and in this situation nothing is different from MP3, WAV, AAC, OGG, etc. There are only a few operations that you can apply to a MP3 stream without decompressing it, mainly volume change, as you can not, in example, remove a block directly from the MP3 stream even if the block is an MP3 frame because each frame is dependent of previous frames and if you remove one an audible "bleep" can happen (high chance). So you only need something to decompress MP3 (and maybe other formats). -- ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] where to find materials about MP3 file format
I have A very big and non easy dream. Making similar MP3 editor like MP3 direct cut for Windows is. But sure! I would like to develop it for Android. And I want to support keyboard letter commands such as inside MP3 directcut for Windows. Sure. I Am not so expert like MR Martin Pesh is. So I must go much more easier way. I want to only develop engine, which will play, stop, will support left and right arrow key as A key for making forward and backward. And especially, and this is The most important, I want to support Block operations to assign beginning of block and its end. And mainly, I want to use remove block command, which will hae immediate effect. So MP3 engine will skip previously non removed data. What do I need? Some technical manual about MP3 format. Sure. Even Android media player will allow Me to play, forward, backward, playand stop. But I must have deep knowledge about MP3 file format structure. So I will be able to remove block. MP3directcut do not remove data directly from existing MP3 file or from temporary copy of this file. It making software magic so software counter, which control The playback simply do not know about previously assigned MP3 part for removal. Removed data are physically stored after user use corresponding save function from menu. Before this, user can remove as much part as he or she wants. To prevent Android crash, I will avoid to use clipboard operations. Android is not Windows and too big data chunks may be cause some memory allocation issues. Who of us would have some tip how to find MP3 file format technical specifications? Pascal support binary file operations. So real data manipulations will begin after user press function save changes. Sure. As MP3 directcut, I will have to use The same approach. I must create copy of original file after user press save and after this copy will be created, I must manipulate with data. I think, that I will have to use array which will contain beginning and end of MP3 data for removal. It will not be easy work. But as I have written previously. I do not have ambitions to create real clone of MP3 direct cut for Android with all of its functions. I want only play, stop, forward, backward while play. MP3 directcut uses frames approach. So I will have to include slider which will allow users to specify number of MP3 frames while backward and forwarding. Existing MP3 editors for Android on Google Play are not comfortable for Me. It do not support keyboard shortcut and it is not possible to remove many parts of MP3 files. Only one selection inside one file. I hope, that PPCJVM compiler contain enoug of internal command to create this tool. Sure. I will use Android Media Player APIS, thanks to creator of Pandroid, I have functioning example how to call it even without crashes and memory allocation leaks. The most difficult part will be to correctly reproduce original MP3 file when saving data without removed MP3 blocks. Sure. Application must be usable also for sighted users so I will not only use keyboard show method without GUI. App will contain The series of Buttons. By The way. Do you know, that Pandroid bundle contain special unit, which will allow you to combine buttons with A nice .png pictures? And GUI look very nicely. You will be able to scroll among many many buttons without crashes. And you will not had to use object position values. But how to achieve The complex algorithm for recreating MP3 file. It will not be easy walk across The park. I will also have to use effective approach to prevent memory allocation problems. I hve analysed Github but there was no useful source codes. May be, that somebody of us would give Me some tips and tricks. I do not want to use Basic, since interpreter machine contain many many lines of Java source code. And I Am convinced, that when I compile app directly to .dex format by using PPCJVM Android JVM target, resulting code would interpret faster than one Millisecond for one command. But I do not know, how to measure so complex thinks. It would be interesting, if somebody, who have created PPCJVM would try to make some scientific measurement on some device. Or do you think, that it will be even much more slower than One Millisecond per one Pascal command? ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
