Ottenere informazioni generali e metadati da file audio-video con le risorse del API di VLC
Con la libreria VLC è possibile anche estrarre da un file multimediale informazioni generali ed evenuali metadati.
E' necessario avere installata nel sistema e richiamare in Gambas la libreria condivisa: "libvlc.so.5.6.0"
Mostriamo un esempio:
Library "libvlc:5.6.0"
Public Struct video_track_t
i_height As Integer
i_width As Integer
i_sar_num As Integer
i_sar_den As Integer
i_frame_rate_num As Integer
i_frame_rate_den As Integer
i_orientation As Integer
i_projection As Integer
pose1 As Single
pose2 As Single
pose3 As Single
pose4 As Single
i_multiview As Byte
End Struct
Public Struct audio_track_t
i_channels As Integer
i_rate As Integer
End Struct
Private Enum libvlc_media_parse_local = 0,
libvlc_media_parse_network,
libvlc_media_fetch_local,
libvlc_media_fetch_network = 4,
libvlc_media_do_interact = 8
' libvlc_instance_t * libvlc_new (int argc, const char *const *argv) ' Create And initialize a libvlc instance. Private Extern libvlc_new(argc As Integer, argv As String[]) As Pointer
' libvlc_media_t * libvlc_media_new_path (libvlc_instance_t *p_instance, const char *path) ' Create a media for a certain file path. Private Extern libvlc_media_new_path(p_instance As Pointer, path As String) As Pointer
' int libvlc_media_parse_with_options (libvlc_media_t *p_md, libvlc_media_parse_flag_t parse_flag, int timeout) ' Parse the media asynchronously with options. Private Extern libvlc_media_parse_with_options(p_md As Pointer, parse_flag As Integer, timeout As Integer) As Integer
' libvlc_time_t libvlc_media_get_duration(libvlc_media_t *p_md) ' Get duration (in ms) of media descriptor object item. Private Extern libvlc_media_get_duration(p_md As Pointer) As Long
' char* libvlc_media_get_meta (libvlc_media_t * p_md, libvlc_meta_t e_meta) ' Read the meta of the media. Private Extern libvlc_media_get_meta(p_md As Pointer, e_meta As Integer) As String
' unsigned libvlc_media_tracks_get (libvlc_media_t * p_md, libvlc_media_track_t *** tracks) ' Get media descriptor's elementary streams description. Private Extern libvlc_media_tracks_get(p_md As Pointer, tracks As Pointer) As Integer
' const char * libvlc_media_get_codec_description (libvlc_track_type_t i_type, uint32_t i_codec) ' Get codec description from media elementary stream. Private Extern libvlc_media_get_codec_description(i_type As Integer, i_codec As Integer) As String
' void libvlc_media_release (libvlc_media_t *p_md) ' Decrement the reference count of a media descriptor object. Private Extern libvlc_media_release(p_md As Pointer)
' libvlc_release (libvlc_instance_t * p_instance) ' Decrement the reference count of a libvlc instance, and destroy it if it reaches zero. Private Extern libvlc_release(p_instance As Pointer)
Public Sub Main()
Dim inst, md, p1, p2 As Pointer
Dim tm As Long
Dim b As Byte
Dim s As String
Dim tp, i As Integer
Dim vt As Video_track_t
Dim at As Audio_track_t
Dim meta As String[] = ["Title:", "Artist:", "Genre", "Copyright:", "Album", "TrackNumber:",
"Description:", "Rating:", "Date:", "Setting:", "URL:",
"Language:", "NowPlaying:", "Publisher:", "EncodedBy:", "ArtworkURL:",
"TrackID:", "TrackTotal:", "Director:", "Season:", "Episode:",
"ShowName:", "Actors:", "AlbumArtist:", "DiscNumber:", "DiscTotal:"]
Dim orient As String[] = ["Normal", "Flipped horizontally", "Flipped vertically", "Rotated 180 degrees",
"Transposed", "Rotated 90 degrees clockwise", "Rotated 90 degrees anti-clockwise", "Anti-transposed"]
s = "/ruta/del/archivo/video"
Print "Nome file: "; s
inst = libvlc_new(0, Null)
md = libvlc_media_new_path(inst, s)
libvlc_media_parse_with_options(md, libvlc_media_parse_local, 0)
Sleep 0.1
tm = libvlc_media_get_duration(md)
Print "Durata: "; Date(0, 0, 0, 0, 0, 0, tm)
Print "\n- Metadati -"
For b = 0 To meta.Max
s = libvlc_media_get_meta(md, b)
If Not IsNull(s) Then Print meta[b]; String(17 - Len(meta[b]), Chr(32)); s
Next
Print "\n- Codificatore -"
p1 = Alloc(24)
p2 = VarPtr(p1)
i = libvlc_media_tracks_get(md, VarPtr(p2))
For b = 0 To i - 1
tp = Int@(Pointer@(p2 + (SizeOf(gb.Pointer) * b)) + 12)
Print "Codifica: "; libvlc_media_get_codec_description(tp, Int@(Pointer@(p2 + (SizeOf(gb.Pointer) * b))))
Print "Tipo media: ";
Select Case tp
Case -1
Print "Unknown"
Case 0
Print "Audio"
at = Pointer@(Pointer@(p2 + (SizeOf(gb.Pointer))) + 24)
With at
Print "Canali: "; at.i_channels
Print "Frequenza camp.: "; at.i_rate
End With
Case 1
Print "Video"
vt = Pointer@(Pointer@(p2) + 24)
With vt
Print "Risoluzione: "; .i_width; "x"; .i_height
Print "Fotogrammi/sec.: "; .i_frame_rate_num
Print "Orientazione: "; orient[.i_orientation]
End With
Case 2
Print "Text"
End Select
Print
Next
' Libera la memoria: Free(p1) libvlc_media_release(md) libvlc_release(inst) End
