Estrarre informazioni da un file MP3 con le funzioni esterne del API di libmpeg3
Da Gambas-it.org - Wikipedia.
Versione del 23 lug 2018 alle 15:58 di Vuott (Discussione | contributi)
Con alcune risorse della libreria esterna "libmpeg3" è possibile ottenere alcune informazioni strettamente relative a un file mp3.
E' necessario avere installata nel sistema operativo e richiamare nel programma Gambas la libreria dinamica condivisa: libmpeg3.so
Mostriamo un semplice esempio:
Library "libmpeg3" Public Struct mpeg3_t fs As Pointer demuxer As Pointer total_astreams As Integer atrack[&010000] As Pointer vtrack[&010000] As Pointer strack[&010000] As Pointer frame_offsets As Pointer sample_offsets As Pointer keyframe_numbers As Pointer video_eof As Pointer audio_eof As Pointer total_frame_offsets As Pointer total_sample_offsets As Pointer total_samples As Pointer total_keyframe_numbers As Pointer channel_counts As Pointer indexes As Pointer total_indexes As Integer index_bytes As Long is_transport_stream As Integer is_program_stream As Integer is_ifo_file As Integer is_audio_stream As Integer is_video_stream As Integer is_bd As Integer packet_size As Integer last_type_read As Integer last_stream_read As Integer subtitle_track As Integer program As Integer cpus As Integer seekable As Integer toc_fd As Pointer byte_pts As Long have_palette As Integer palette[64] As Byte source_date As Long End Struct ' int mpeg3_check_sig(char *path) ' Check for file compatibility. Private Extern mpeg3_check_sig(path As String) As Integer ' mpeg3_t* mpeg3_open(char *path, int *error_return) ' Open the MPEG stream. Private Extern mpeg3_open(path As String, error_return As Pointer) As mpeg3_t ' int64_t mpeg3_get_bytes(mpeg3_t *file) ' Total bytes. Private Extern mpeg3_get_bytes(mpeg3file As mpeg3_t) As Long ' int mpeg3_audio_channels(mpeg3_t *file, int stream) Private Extern mpeg3_audio_channels(mpeg3file As mpeg3_t, _stream As Integer) As Integer ' int mpeg3_sample_rate(mpeg3_t *file, int stream) Private Extern mpeg3_sample_rate(mpeg3file As mpeg3_t, _stream As Integer) As Integer ' char* mpeg3_audio_format(mpeg3_t *file, int stream) Private Extern mpeg3_audio_format(mpeg3file As mpeg3_t, _stream As Integer) As Pointer ' long mpeg3_audio_samples(mpeg3_t *file, int stream) Private Extern mpeg3_audio_samples(mpeg3file As mpeg3_t, _stream As Integer) As Long ' int mpeg3_close(mpeg3_t *file) Private Extern mpeg3_close(mpeg3file As mpeg3_t) As Integer Public Sub Main() Dim perc As String Dim i, freq As Integer Dim cmp As Long Dim mp3 As mpeg3_t perc = "/percorso/del/file.mp3" i = mpeg3_check_sig(perc) If i = 0 Then Error.Raise("Tipo file incompatibile !") mp3 = mpeg3_open(perc, 0) i = mpeg3_total_astreams(mp3) Print "File audio: "; perc Print "Dimensione: "; mpeg3_get_bytes(mp3); " byte" Print "Numero canali: "; mpeg3_audio_channels(mp3, 0) freq = mpeg3_sample_rate(mp3, 0) Print "Frequenza: "; freq; " hertz" Print "Formato audio: "; String@(mpeg3_audio_format(mp3, 0)) cmp = mpeg3_audio_samples(mp3, 0) Print "Campioni audio: "; cmp; " byte" Print "Durata: "; CStr(Date(0, 0, 0, 0, 0, 0, (cmp / freq) * 1000)) mpeg3_close(mp3) End