[vlc-commits] commit: Support DVD LPCM encode. (Steinar H. Gunderson )
git at videolan.org
git at videolan.org
Fri Oct 8 23:36:57 CEST 2010
vlc | branch: master | Steinar H. Gunderson <steinar+vlc at gunderson.no> | Sun Sep 26 00:24:09 2010 +0200| [4b103b8440fb8dbbe40ace739927d26795bbc2e1] | committer: Rémi Denis-Courmont
Support DVD LPCM encode.
This patch adds encode support to the LPCM module; only the DVD variant for
now. It's not been tested with any other clients than VLC.
The rationale for this functionality is relatively simple -- LPCM is
currently the only low-latency codec that VLC supports and that can be
embedded in a TS stream. Longer-term support for other low-latency codecs
would be good, but if you're not particularly bandwidth-constrained and need
low latency, this is currently the best option I know of.
Signed-off-by: Rémi Denis-Courmont <remi at remlab.net>
> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=4b103b8440fb8dbbe40ace739927d26795bbc2e1
---
modules/codec/lpcm.c | 188 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 188 insertions(+), 0 deletions(-)
diff --git a/modules/codec/lpcm.c b/modules/codec/lpcm.c
index 3928065..1360a4f 100644
--- a/modules/codec/lpcm.c
+++ b/modules/codec/lpcm.c
@@ -9,6 +9,7 @@
* Christophe Massiot <massiot at via.ecp.fr>
* Gildas Bazin <gbazin at videolan.org>
* Lauren Aimar <fenrir _AT_ videolan _DOT_ org >
+ * Steinar H. Gunderson <steinar+vlc at gunderson.no>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -45,6 +46,12 @@ static int OpenDecoder ( vlc_object_t * );
static int OpenPacketizer( vlc_object_t * );
static void CloseCommon ( vlc_object_t * );
+#ifdef ENABLE_SOUT
+static int OpenEncoder ( vlc_object_t * );
+static void CloseEncoder ( vlc_object_t * );
+static block_t *EncodeFrames( encoder_t *, aout_buffer_t * );
+#endif
+
vlc_module_begin ()
set_category( CAT_INPUT )
@@ -58,6 +65,14 @@ vlc_module_begin ()
set_capability( "packetizer", 100 )
set_callbacks( OpenPacketizer, CloseCommon )
+#ifdef ENABLE_SOUT
+ add_submodule ()
+ set_description( N_("Linear PCM audio encoder") )
+ set_capability( "encoder", 100 )
+ set_callbacks( OpenEncoder, CloseEncoder )
+ add_shortcut( "lpcm" )
+#endif
+
vlc_module_end ()
@@ -79,6 +94,19 @@ struct decoder_sys_t
int i_type;
};
+#ifdef ENABLE_SOUT
+struct encoder_sys_t
+{
+ int i_channels;
+ int i_rate;
+
+ int i_frame_samples;
+ uint8_t *p_buffer;
+ int i_buffer_used;
+ int i_frame_num;
+};
+#endif
+
/*
* LPCM DVD header :
* - number of frames in this packet (8 bits)
@@ -399,6 +427,166 @@ static void CloseCommon( vlc_object_t *p_this )
free( p_dec->p_sys );
}
+#ifdef ENABLE_SOUT
+/*****************************************************************************
+ * OpenEncoder: lpcm encoder construction
+ *****************************************************************************/
+static int OpenEncoder( vlc_object_t *p_this )
+{
+ encoder_t *p_enc = (encoder_t *)p_this;
+ encoder_sys_t *p_sys;
+
+ /* We only support DVD LPCM yet. */
+ if( p_enc->fmt_out.i_codec != VLC_CODEC_DVD_LPCM )
+ return VLC_EGENERIC;
+
+ if( p_enc->fmt_in.audio.i_rate != 48000 &&
+ p_enc->fmt_in.audio.i_rate != 96000 &&
+ p_enc->fmt_in.audio.i_rate != 44100 &&
+ p_enc->fmt_in.audio.i_rate != 32000 )
+ {
+ msg_Err( p_enc, "DVD LPCM supports only sample rates of 48, 96, 44.1 or 32 kHz" );
+ return VLC_EGENERIC;
+ }
+
+ if( p_enc->fmt_in.audio.i_channels > 8 )
+ {
+ msg_Err( p_enc, "DVD LPCM supports a maximum of eight channels" );
+ return VLC_EGENERIC;
+ }
+
+ /* Allocate the memory needed to store the encoder's structure */
+ if( ( p_enc->p_sys = p_sys =
+ (encoder_sys_t *)malloc(sizeof(encoder_sys_t)) ) == NULL )
+ return VLC_ENOMEM;
+
+ /* In DVD LCPM, a frame is always 150 PTS ticks. */
+ p_sys->i_frame_samples = p_enc->fmt_in.audio.i_rate * 150 / 90000;
+ p_sys->p_buffer = (uint8_t *)malloc(
+ p_sys->i_frame_samples *
+ p_enc->fmt_in.audio.i_channels *
+ p_enc->fmt_in.audio.i_bitspersample);
+ p_sys->i_buffer_used = 0;
+ p_sys->i_frame_num = 0;
+
+ p_sys->i_channels = p_enc->fmt_in.audio.i_channels;
+ p_sys->i_rate = p_enc->fmt_in.audio.i_rate;
+
+ p_enc->pf_encode_audio = EncodeFrames;
+ p_enc->fmt_in.i_codec = p_enc->fmt_out.i_codec;
+
+ p_enc->fmt_in.audio.i_bitspersample = 16;
+ p_enc->fmt_in.i_codec = VLC_CODEC_S16B;
+
+ p_enc->fmt_out.i_bitrate =
+ p_enc->fmt_in.audio.i_channels *
+ p_enc->fmt_in.audio.i_rate *
+ p_enc->fmt_in.audio.i_bitspersample *
+ (p_sys->i_frame_samples + LPCM_VOB_HEADER_LEN) /
+ p_sys->i_frame_samples;
+
+ return VLC_SUCCESS;
+}
+
+/*****************************************************************************
+ * CloseEncoder: lpcm encoder destruction
+ *****************************************************************************/
+static void CloseEncoder ( vlc_object_t *p_this )
+{
+ encoder_t *p_enc = (encoder_t *)p_this;
+ encoder_sys_t *p_sys = p_enc->p_sys;
+
+ free( p_sys->p_buffer );
+ free( p_sys );
+}
+
+/*****************************************************************************
+ * EncodeFrames: encode zero or more LCPM audio packets
+ *****************************************************************************/
+static block_t *EncodeFrames( encoder_t *p_enc, aout_buffer_t *p_aout_buf )
+{
+ encoder_sys_t *p_sys = p_enc->p_sys;
+ block_t *p_first_block = NULL, *p_last_block = NULL;
+
+ if( !p_aout_buf || !p_aout_buf->i_buffer ) return NULL;
+
+ const int i_num_frames = ( p_sys->i_buffer_used + p_aout_buf->i_nb_samples ) /
+ p_sys->i_frame_samples;
+ const int i_leftover_samples = ( p_sys->i_buffer_used + p_aout_buf->i_nb_samples ) %
+ p_sys->i_frame_samples;
+ const int i_frame_size = p_sys->i_frame_samples * p_sys->i_channels * 2 + LPCM_VOB_HEADER_LEN;
+ const int i_start_offset = -p_sys->i_buffer_used;
+
+ uint8_t i_freq_code = 0;
+
+ switch( p_sys->i_rate ) {
+ case 48000:
+ i_freq_code = 0;
+ break;
+ case 96000:
+ i_freq_code = 1;
+ break;
+ case 44100:
+ i_freq_code = 2;
+ break;
+ case 32000:
+ i_freq_code = 3;
+ break;
+ default:
+ assert(0);
+ }
+
+ int i_bytes_consumed = 0;
+
+ for ( int i = 0; i < i_num_frames; ++i )
+ {
+ block_t *p_block = block_New( p_enc, i_frame_size );
+ if( !p_block )
+ return NULL;
+
+ uint8_t *frame = (uint8_t *)p_block->p_buffer;
+ frame[0] = 1; /* one frame in packet */
+ frame[1] = 0;
+ frame[2] = 0; /* no first access unit */
+ frame[3] = (p_sys->i_frame_num + i) & 0x1f; /* no emphasis, no mute */
+ frame[4] = (i_freq_code << 4) | (p_sys->i_channels - 1);
+ frame[5] = 0x80; /* neutral dynamic range */
+
+ const int i_consume_samples = p_sys->i_frame_samples - p_sys->i_buffer_used;
+ const int i_kept_bytes = p_sys->i_buffer_used * p_sys->i_channels * 2;
+ const int i_consume_bytes = i_consume_samples * p_sys->i_channels * 2;
+
+ memcpy( frame + 6, p_sys->p_buffer, i_kept_bytes );
+ memcpy( frame + 6 + i_kept_bytes, p_aout_buf->p_buffer + i_bytes_consumed, i_consume_bytes );
+
+ p_sys->i_frame_num++;
+ p_sys->i_buffer_used = 0;
+ i_bytes_consumed += i_consume_bytes;
+
+ /* We need to find i_length by means of next_pts due to possible roundoff errors. */
+ mtime_t this_pts = p_aout_buf->i_pts +
+ (i * p_sys->i_frame_samples + i_start_offset) * CLOCK_FREQ / p_sys->i_rate;
+ mtime_t next_pts = p_aout_buf->i_pts +
+ ((i + 1) * p_sys->i_frame_samples + i_start_offset) * CLOCK_FREQ / p_sys->i_rate;
+
+ p_block->i_pts = p_block->i_dts = this_pts;
+ p_block->i_length = next_pts - this_pts;
+
+ if( !p_first_block )
+ p_first_block = p_last_block = p_block;
+ else
+ p_last_block = p_last_block->p_next = p_block;
+ }
+
+ memcpy( p_sys->p_buffer,
+ p_aout_buf->p_buffer + i_bytes_consumed,
+ i_leftover_samples * p_sys->i_channels * 2 );
+ p_sys->i_buffer_used = i_leftover_samples;
+
+ return p_first_block;
+}
+#endif
+
/*****************************************************************************
*
*****************************************************************************/
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