Mercurial > SDL_sound_CoreAudio
changeset 96:25e515dfa18d
Fix for MP3 detection.
author | Ryan C. Gordon <icculus@icculus.org> |
---|---|
date | Tue, 02 Oct 2001 17:46:12 +0000 |
parents | 4436f4587c9a |
children | 40be84c1aadd |
files | decoders/mp3.c |
diffstat | 1 files changed, 39 insertions(+), 14 deletions(-) [+] |
line wrap: on
line diff
--- a/decoders/mp3.c Tue Oct 02 17:23:08 2001 +0000 +++ b/decoders/mp3.c Tue Oct 02 17:46:12 2001 +0000 @@ -101,25 +101,49 @@ SDL_AudioSpec spec; Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; SDL_RWops *refCounter; - Uint8 mp3_magic[2]; output_version(); /* - * SMPEG appears to be far too greedy about what it accepts as input. - * This test was adapted from SDL_mixer. + * If I understand things correctly, MP3 files don't really have any + * magic header we can check for. The MP3 player is expected to just + * pick the first thing that looks like a valid frame and start + * playing from there. + * + * So here's what we do: If the caller insists that this is really + * MP3 we'll take his word for it. Otherwise, use the same test as + * SDL_mixer does and check if the stream starts with something that + * looks like a frame. + * + * A frame begins with 11 bits of frame sync (all bits must be set), + * followed by a two-bit MPEG Audio version ID: + * + * 00 - MPEG Version 2.5 (later extension of MPEG 2) + * 01 - reserved + * 10 - MPEG Version 2 (ISO/IEC 13818-3) + * 11 - MPEG Version 1 (ISO/IEC 11172-3) + * + * Apparently we don't handle MPEG Version 2.5. */ - if (SDL_RWread(internal->rw, mp3_magic, sizeof (mp3_magic), 1) != 1) + if (__Sound_strcasecmp(ext, "MP3") != 0) { - Sound_SetError("MP3: Could not read MP3 magic."); - return(0); - } - if (mp3_magic[0] != 0xFF || (mp3_magic[1] & 0xF0) != 0xF0) - { - Sound_SetError("MP3: Not an MP3 stream."); - return(0); - } - SDL_RWseek(internal->rw, -sizeof (mp3_magic), SEEK_CUR); + Uint8 mp3_magic[2]; + + if (SDL_RWread(internal->rw, mp3_magic, sizeof (mp3_magic), 1) != 1) + { + Sound_SetError("MP3: Could not read MP3 magic."); + return(0); + } /*if */ + + if (mp3_magic[0] != 0xFF || (mp3_magic[1] & 0xF0) != 0xF0) + { + Sound_SetError("MP3: Not an MP3 stream."); + return(0); + } /* if */ + + /* !!! FIXME: If the seek fails, we'll probably miss a frame */ + SDL_RWseek(internal->rw, -sizeof (mp3_magic), SEEK_CUR); + } /* if */ refCounter = RWops_RWRefCounter_new(internal->rw); if (refCounter == NULL) @@ -171,8 +195,9 @@ SMPEG_loop(smpeg, 0); SMPEG_wantedSpec(smpeg, &spec); + /* - * One of the MP3:s I tried wouldn't work unless I added this line + * One of the MP3s I tried wouldn't work unless I added this line * to tell SMPEG that yes, it may have the spec it wants. */ SMPEG_actualSpec(smpeg, &spec);