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参数： lpFilename：指向 MP3 文件名的指针，用于从 中获取信息 lpInfoStruct： 指向将在返回 时接收信息的MP3INFO结构的指针 此功能扫描整个 MP3 并计算比特率、时间和其他一些信息。 MP3INFO STRUCT fileSize：MP3 文件的大小 fileLength：文件 的长度，单位为毫秒 bitrate： 比特率，单位为位/秒。此值可以为负数，在这种情况下，mp3 具有可变比特率。该值是平均比特率，已否定。 频率：MP3 的频率，单位为赫兹（44100、22050 等） nFrames：MPEG 帧数。注意：不要依赖此值，它并不总是正确的（还）。 MP3INFO完 该过程针对大小进行了优化。 返回： 失败时为 false，否则为 true .data ;V1 layer 3 bitrates bitrateTableV1 dw -1,32,40,48,56,64,80,96,112,128,160,192,224,256,320,-1 ;V2/2.5 layer 3 bitrates bitrateTableV2 dw -1,8,16,24,32,40,48,56,64,80,96,112,128,144,160,-1 samplerateTableV1 dw 44100,48000,32000 samplerateTableV2 dw 22050,24000,16000 samplerateTableV2_5 dw 11025,12000,8000 .code MP3INFO STRUCT fileSize dword ? ; in bytes fileLength dword ? ; in miliseconds bitrate sdword ? ; in bps. if negative: ; variable bitrate,bitrate=negated average frequency dword ? ; in Hertz nFrames dword ? ; number of MPEG frames. ; Note: do not rely on this value, ; it isn't always correct (yet). MP3INFO ENDS GetMP3Info proc uses esi edi ebx lpFilename:DWORD, lpInfoStruct:DWORD LOCAL hFile:DWORD LOCAL hMap:DWORD LOCAL pMap:DWORD LOCAL totalbitrate:DWORD LOCAL srTablePtr:DWORD xor ebx, ebx mov hFile, ebx mov hMap, ebx mov pMap, ebx mov edi, lpInfoStruct push edi or eax, -1 mov ecx, (sizeof MP3INFO) / 4 rep stosd mov totalbitrate, ebx assume edi:PTR MP3INFO pop edi mov [edi].nFrames, ebx invoke CreateFile, lpFilename, GENERIC_READ, FILE_SHARE_READ, ebx, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN OR FILE_FLAG_NO_BUFFERING, ebx cmp eax, INVALID_HANDLE_VALUE je _invalid mov hFile, eax invoke CreateFileMapping, eax, ebx, PAGE_READONLY, ebx,ebx,ebx or eax, eax jz _invalid mov hMap, eax invoke MapViewOfFile, eax, FILE_MAP_READ,ebx,ebx,ebx or eax, eax jz _invalid mov pMap, eax mov esi, eax invoke GetFileSize, hFile, NULL mov [edi].fileSize, eax lea ebx, [eax+esi] _gotonextframe: ; find first 8 bits of sync bits cmp byte ptr [esi], 0FFh je @F inc esi cmp esi, ebx jb _gotonextframe jmp _done ;possible first 8 sync bits found @@: inc esi cmp esi, ebx jae _done mov al, [esi] mov cl, al and cl, 11100000b cmp cl, 11100000b jne _gotonextframe inc esi _frame_found: mov cl, al and cl, 00011110b mov edx, offset bitrateTableV1 mov srTablePtr, offset samplerateTableV1 cmp cl, 00011010b ;MPEG v1, layer 3? je _frame_continue mov edx, offset bitrateTableV2 mov srTablePtr, offset samplerateTableV2 cmp cl, 00010010b ;MPEG v2, layer 3? je _frame_continue mov srTablePtr, offset samplerateTableV2_5 cmp cl, 00000010b ;MPEG v2.5, layer 3 jne _gotonextframe ;find next frame PrintText "falling" ;fall through... _frame_continue: PrintText "---frame continue---" mov eax, ebx sub eax, esi cmp eax, 2 ;at least 2 bytes readable? jb _done movzx eax, byte ptr [esi] mov ecx, eax shr al, 4 movsx eax, word ptr [edx][2*eax] cmp eax, -1 je _gotonextframe sub esi, 2 ;point back to start of frame, as framesize is added later ; eax is bitrate add totalbitrate, eax mov edx, [edi].bitrate cmp edx, -1 jne _bitrate_already_set mov [edi].bitrate, eax jmp _fixed_bitrate_so_far _bitrate_already_set: cmp eax, edx ;current bitrate same as set bitrate? je _fixed_bitrate_so_far ;variable bitrate and [edi].bitrate, 0 ;set to zero indicating variable bitrate ;fall through... _fixed_bitrate_so_far: xor edx, edx ; init framesize to zero shr ecx, 2 setc dl ;last bit shifted out is padding bit, ; if set increase framesize by one and ecx, 3 cmp ecx, 3 jne @F inc esi cmp esi, ebx jae _done jmp _gotonextframe @@: shl ecx, 1 add ecx, srTablePtr movzx ecx, word ptr [ecx] mov [edi].frequency, ecx ;FrameSize = 144 * BitRate / SampleRate + Padding ; eax = bitrate(in kbps, needs to be converted to bps yet) ; ecx = sampleRate ; edx = padding ; framesize = 144 * eax / ecx + edx push edx mov edx, 144*1000 cmp srTablePtr, offset samplerateTableV1 je @F mov edx, 72*1000 @@: mul edx div ecx pop edx add edx, eax ; edx is framesize now add esi, edx cmp esi, ebx jae _done ; frame bigger than file, file is cut inc [edi].nFrames jmp _gotonextframe _invalid: xor eax, eax jmp _exit _done: mov ebx, 1000 mov ecx, [edi].nFrames ;get number of frames mov eax, [edi].bitrate ;get bitrate in kbps mul ebx ;*1000, in bpsd mov [edi].bitrate, eax ;set new bitrate, in bps or eax, eax ;bitrate zero? jnz _fixed_bitrate ;if not, fixed mov eax, totalbitrate ;else, variable. get total (sum of all bitrates) mul ebx ;multiple by 1000 or ecx, ecx ;no frames? jz _invalid ;bye div ecx ;divide by number of frames neg eax ;negate, indicating a variable bitrate mov [edi].bitrate, eax _fixed_bitrate: ; 1152 = # of samples in one frame for layer 3 mpegs mov ebx, 1152*1000 mov eax, [edi].nFrames xor edx, edx mul ebx mov ebx, [edi].frequency or ebx, ebx jz _invalid div ebx mov [edi].fileLength, eax ;set filelengths, in msecs ;calculate time ;bitrate assume edi:nothing xor eax, eax inc eax _exit: push eax mov eax, pMap or eax, eax jz @F invoke UnmapViewOfFile, eax @@: mov eax, hMap or eax, eax jz @F invoke CloseHandle, eax @@: mov eax, hFile or eax, eax jz @F invoke CloseHandle, eax @@: pop eax ret GetMP3Info endp