FFmpeg
decode_simple.c
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1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 /* shared code for simple demux/decode tools */
20 
21 #include <stdlib.h>
22 #include <string.h>
23 
24 #include "decode_simple.h"
25 
26 #include "libavformat/avformat.h"
27 
28 #include "libavcodec/avcodec.h"
29 #include "libavcodec/packet.h"
30 
31 #include "libavutil/dict.h"
32 #include "libavutil/error.h"
33 #include "libavutil/frame.h"
34 
35 static int decode_read(DecodeContext *dc, int flush)
36 {
37  const int ret_done = flush ? AVERROR_EOF : AVERROR(EAGAIN);
38  int ret = 0;
39 
40  while (ret >= 0 &&
41  (dc->max_frames == 0 || dc->decoder->frame_number < dc->max_frames)) {
42  ret = avcodec_receive_frame(dc->decoder, dc->frame);
43  if (ret < 0) {
44  if (ret == AVERROR_EOF) {
45  int err = dc->process_frame(dc, NULL);
46  if (err < 0)
47  return err;
48  }
49 
50  return (ret == ret_done) ? 0 : ret;
51  }
52 
53  ret = dc->process_frame(dc, dc->frame);
55  if (ret < 0)
56  return ret;
57 
58  if (dc->max_frames && dc->decoder->frame_number == dc->max_frames)
59  return 1;
60  }
61 
62  return (dc->max_frames == 0 || dc->decoder->frame_number < dc->max_frames) ? 0 : 1;
63 }
64 
66 {
67  int ret;
68 
69  ret = avcodec_open2(dc->decoder, NULL, &dc->decoder_opts);
70  if (ret < 0)
71  return ret;
72 
73  while (ret >= 0) {
74  ret = av_read_frame(dc->demuxer, dc->pkt);
75  if (ret < 0)
76  goto flush;
77  if (dc->pkt->stream_index != dc->stream->index) {
78  av_packet_unref(dc->pkt);
79  continue;
80  }
81 
82  ret = avcodec_send_packet(dc->decoder, dc->pkt);
83  if (ret < 0) {
84  fprintf(stderr, "Error decoding: %d\n", ret);
85  return ret;
86  }
87  av_packet_unref(dc->pkt);
88 
89  ret = decode_read(dc, 0);
90  if (ret < 0) {
91  fprintf(stderr, "Error decoding: %d\n", ret);
92  return ret;
93  } else if (ret > 0)
94  return 0;
95  }
96 
97 flush:
98  avcodec_send_packet(dc->decoder, NULL);
99  ret = decode_read(dc, 1);
100  if (ret < 0) {
101  fprintf(stderr, "Error flushing: %d\n", ret);
102  return ret;
103  }
104 
105  return 0;
106 }
107 
109 {
110  av_dict_free(&dc->decoder_opts);
111 
113  av_packet_free(&dc->pkt);
114 
115  avcodec_free_context(&dc->decoder);
116  avformat_close_input(&dc->demuxer);
117 }
118 
119 int ds_open(DecodeContext *dc, const char *url, int stream_idx)
120 {
121  const AVCodec *codec;
122  int ret;
123 
124  memset(dc, 0, sizeof(*dc));
125 
126  dc->pkt = av_packet_alloc();
127  dc->frame = av_frame_alloc();
128  if (!dc->pkt || !dc->frame) {
129  ret = AVERROR(ENOMEM);
130  goto fail;
131  }
132 
133  ret = avformat_open_input(&dc->demuxer, url, NULL, NULL);
134  if (ret < 0) {
135  fprintf(stderr, "Error opening input file: %d\n", ret);
136  return ret;
137  }
138 
139  if (stream_idx < 0 || stream_idx >= dc->demuxer->nb_streams)
140  return AVERROR(EINVAL);
141 
142  dc->stream = dc->demuxer->streams[stream_idx];
143 
144  codec = avcodec_find_decoder(dc->stream->codecpar->codec_id);
145  if (!codec)
147 
148  dc->decoder = avcodec_alloc_context3(codec);
149  if (!dc->decoder)
150  return AVERROR(ENOMEM);
151 
152  return 0;
153 
154 fail:
155  ds_free(dc);
156  return ret;
157 }
av_packet_unref
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:417
AVCodec
AVCodec.
Definition: codec.h:202
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
AVERROR_EOF
#define AVERROR_EOF
End of file.
Definition: error.h:57
av_frame_free
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:112
av_read_frame
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
Definition: demux.c:1414
av_packet_free
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
Definition: avpacket.c:75
decode_read
static int decode_read(DecodeContext *dc, int flush)
Definition: decode_simple.c:35
ds_open
int ds_open(DecodeContext *dc, const char *url, int stream_idx)
Definition: decode_simple.c:119
avformat_close_input
void avformat_close_input(AVFormatContext **s)
Close an opened input AVFormatContext.
Definition: demux.c:355
fail
#define fail()
Definition: checkasm.h:127
ds_run
int ds_run(DecodeContext *dc)
Definition: decode_simple.c:65
av_frame_alloc
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:99
avformat_open_input
int avformat_open_input(AVFormatContext **ps, const char *url, const AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
Definition: demux.c:207
avcodec_alloc_context3
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition: options.c:141
avcodec_receive_frame
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder.
Definition: decode.c:643
NULL
#define NULL
Definition: coverity.c:32
flush
static void flush(AVCodecContext *avctx)
Definition: aacdec_template.c:593
avcodec_free_context
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
Definition: options.c:156
avcodec_open2
int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Definition: avcodec.c:137
error.h
avcodec_find_decoder
const AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
Definition: allcodecs.c:919
dc
Tag MUST be and< 10hcoeff half pel interpolation filter coefficients, hcoeff[0] are the 2 middle coefficients[1] are the next outer ones and so on, resulting in a filter like:...eff[2], hcoeff[1], hcoeff[0], hcoeff[0], hcoeff[1], hcoeff[2] ... the sign of the coefficients is not explicitly stored but alternates after each coeff and coeff[0] is positive, so ...,+,-,+,-,+,+,-,+,-,+,... hcoeff[0] is not explicitly stored but found by subtracting the sum of all stored coefficients with signs from 32 hcoeff[0]=32 - hcoeff[1] - hcoeff[2] - ... a good choice for hcoeff and htaps is htaps=6 hcoeff={40,-10, 2} an alternative which requires more computations at both encoder and decoder side and may or may not be better is htaps=8 hcoeff={42,-14, 6,-2}ref_frames minimum of the number of available reference frames and max_ref_frames for example the first frame after a key frame always has ref_frames=1spatial_decomposition_type wavelet type 0 is a 9/7 symmetric compact integer wavelet 1 is a 5/3 symmetric compact integer wavelet others are reserved stored as delta from last, last is reset to 0 if always_reset||keyframeqlog quality(logarithmic quantizer scale) stored as delta from last, last is reset to 0 if always_reset||keyframemv_scale stored as delta from last, last is reset to 0 if always_reset||keyframe FIXME check that everything works fine if this changes between framesqbias dequantization bias stored as delta from last, last is reset to 0 if always_reset||keyframeblock_max_depth maximum depth of the block tree stored as delta from last, last is reset to 0 if always_reset||keyframequant_table quantization tableHighlevel bitstream structure:==============================--------------------------------------------|Header|--------------------------------------------|------------------------------------|||Block0||||split?||||yes no||||......... intra?||||:Block01 :yes no||||:Block02 :....... ..........||||:Block03 ::y DC ::ref index:||||:Block04 ::cb DC ::motion x :||||......... :cr DC ::motion y :||||....... ..........|||------------------------------------||------------------------------------|||Block1|||...|--------------------------------------------|------------ ------------ ------------|||Y subbands||Cb subbands||Cr subbands||||--- ---||--- ---||--- ---|||||LL0||HL0||||LL0||HL0||||LL0||HL0|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||LH0||HH0||||LH0||HH0||||LH0||HH0|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||HL1||LH1||||HL1||LH1||||HL1||LH1|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||HH1||HL2||||HH1||HL2||||HH1||HL2|||||...||...||...|||------------ ------------ ------------|--------------------------------------------Decoding process:=================------------|||Subbands|------------||||------------|Intra DC||||LL0 subband prediction ------------|\ Dequantization ------------------- \||Reference frames|\ IDWT|------- -------|Motion \|||Frame 0||Frame 1||Compensation . OBMC v -------|------- -------|--------------. \------> Frame n output Frame Frame<----------------------------------/|...|------------------- Range Coder:============Binary Range Coder:------------------- The implemented range coder is an adapted version based upon "Range encoding: an algorithm for removing redundancy from a digitised message." by G. N. N. Martin. The symbols encoded by the Snow range coder are bits(0|1). The associated probabilities are not fix but change depending on the symbol mix seen so far. bit seen|new state ---------+----------------------------------------------- 0|256 - state_transition_table[256 - old_state];1|state_transition_table[old_state];state_transition_table={ 0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 190, 191, 192, 194, 194, 195, 196, 197, 198, 199, 200, 201, 202, 202, 204, 205, 206, 207, 208, 209, 209, 210, 211, 212, 213, 215, 215, 216, 217, 218, 219, 220, 220, 222, 223, 224, 225, 226, 227, 227, 229, 229, 230, 231, 232, 234, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 248, 0, 0, 0, 0, 0, 0, 0};FIXME Range Coding of integers:------------------------- FIXME Neighboring Blocks:===================left and top are set to the respective blocks unless they are outside of the image in which case they are set to the Null block top-left is set to the top left block unless it is outside of the image in which case it is set to the left block if this block has no larger parent block or it is at the left side of its parent block and the top right block is not outside of the image then the top right block is used for top-right else the top-left block is used Null block y, cb, cr are 128 level, ref, mx and my are 0 Motion Vector Prediction:=========================1. the motion vectors of all the neighboring blocks are scaled to compensate for the difference of reference frames scaled_mv=(mv *(256 *(current_reference+1)/(mv.reference+1))+128)> the median of the scaled top and top right vectors is used as motion vector prediction the used motion vector is the sum of the predictor and(mvx_diff, mvy_diff) *mv_scale Intra DC Prediction block[y][x] dc[1]
Definition: snow.txt:400
frame.h
av_packet_alloc
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition: avpacket.c:64
av_dict_free
void av_dict_free(AVDictionary **pm)
Free all the memory allocated for an AVDictionary struct and all keys and values.
Definition: dict.c:203
avcodec_send_packet
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
Definition: decode.c:580
packet.h
av_frame_unref
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
Definition: frame.c:437
Frame::frame
AVFrame * frame
Definition: ffplay.c:154
avcodec.h
ret
ret
Definition: filter_design.txt:187
avformat.h
dict.h
AVERROR_DECODER_NOT_FOUND
#define AVERROR_DECODER_NOT_FOUND
Decoder not found.
Definition: error.h:54
ds_free
void ds_free(DecodeContext *dc)
Definition: decode_simple.c:108
decode_simple.h
DecodeContext
Definition: decode_simple.h:33