libavformat/prompeg.c - third_party/ffmpeg - Git at Google

 /*
  * Pro-MPEG Code of Practice #3 Release 2 FEC
  * Copyright (c) 2016 Mobibase, France (http://www.mobibase.com)
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */

 /**
  * @file
  * Pro-MPEG Code of Practice #3 Release 2 FEC protocol
  * @author Vlad Tarca <vlad.tarca@gmail.com>
  */

 /*
  * Reminder:

  [RFC 2733] FEC Packet Structure

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         RTP Header                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         FEC Header                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         FEC Payload                           |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


  [RFC 3550] RTP header

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |V=2|P|X|  CC   |M|     PT      |       sequence number         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           timestamp                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           synchronization source (SSRC) identifier            |
    +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
    |            contributing source (CSRC) identifiers             |
    |                             ....                              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  [RFC 3550] RTP header extension (after CSRC)

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      defined by profile       |           length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        header extension                       |
    |                             ....                              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  [Pro-MPEG COP3] FEC Header

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      SNBase low bits          |        length recovery        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |E| PT recovery |                 mask                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          TS recovery                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |X|D|type |index|    offset     |      NA       |SNBase ext bits|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  */

 #include "libavutil/avstring.h"
 #include "libavutil/intreadwrite.h"
 #include "libavutil/opt.h"
 #include "libavutil/parseutils.h"
 #include "libavutil/random_seed.h"
 #include "avformat.h"
 #include "config.h"
 #include "url.h"

 #define PROMPEG_RTP_PT 0x60
 #define PROMPEG_FEC_COL 0x0
 #define PROMPEG_FEC_ROW 0x1

 typedef struct PrompegFec {
     uint16_t sn;
     uint32_t ts;
     uint8_t *bitstring;
 } PrompegFec;

 typedef struct PrompegContext {
     const AVClass *class;
     URLContext *fec_col_hd, *fec_row_hd;
     PrompegFec **fec_arr, **fec_col_tmp, **fec_col, *fec_row;
     int ttl;
     uint8_t l, d;
     uint8_t *rtp_buf;
     uint16_t rtp_col_sn, rtp_row_sn;
     uint16_t length_recovery;
     int packet_size;
     int packet_idx, packet_idx_max;
     int fec_arr_len;
     int bitstring_size;
     int rtp_buf_size;
     int init;
     int first;
 } PrompegContext;

 #define OFFSET(x) offsetof(PrompegContext, x)
 #define E AV_OPT_FLAG_ENCODING_PARAM

 static const AVOption options[] = {
     { "ttl",   "Time to live (in milliseconds, multicast only)", OFFSET(ttl), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX, .flags = E },
     { "l", "FEC L", OFFSET(l), AV_OPT_TYPE_INT, { .i64 =  5 }, 4, 20, .flags = E },
     { "d", "FEC D", OFFSET(d), AV_OPT_TYPE_INT, { .i64 =  5 }, 4, 20, .flags = E },
     { NULL }
 };

 static const AVClass prompeg_class = {
     .class_name = "prompeg",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
 };

 static void xor_fast(const uint8_t *in1, const uint8_t *in2, uint8_t *out, int size) {
     int i, n, s;

 #if HAVE_FAST_64BIT
     uint64_t v1, v2;

     n = size / sizeof (uint64_t);
     s = n * sizeof (uint64_t);

     for (i = 0; i < n; i++) {
         v1 = AV_RN64A(in1);
         v2 = AV_RN64A(in2);
         AV_WN64A(out, v1 ^ v2);
         in1 += 8;
         in2 += 8;
         out += 8;
     }
 #else
     uint32_t v1, v2;

     n = size / sizeof (uint32_t);
     s = n * sizeof (uint32_t);

     for (i = 0; i < n; i++) {
         v1 = AV_RN32A(in1);
         v2 = AV_RN32A(in2);
         AV_WN32A(out, v1 ^ v2);
         in1 += 4;
         in2 += 4;
         out += 4;
     }
 #endif

     n = size - s;

     for (i = 0; i < n; i++) {
         out[i] = in1[i] ^ in2[i];
     }
 }

 static int prompeg_create_bitstring(URLContext *h, const uint8_t *buf, int size,
         uint8_t **bitstring) {
     PrompegContext *s = h->priv_data;
     uint8_t *b;

     if (size < 12 || (buf[0] & 0xc0) != 0x80 || (buf[1] & 0x7f) != 0x21) {
         av_log(h, AV_LOG_ERROR, "Unsupported stream format (expected MPEG-TS over RTP)\n");
         return AVERROR(EINVAL);
     }
     if (size != s->packet_size) {
         av_log(h, AV_LOG_ERROR, "The RTP packet size must be constant (set pkt_size)\n");
         return AVERROR(EINVAL);
     }

     *bitstring = av_malloc(s->bitstring_size);
     if (!*bitstring) {
         av_log(h, AV_LOG_ERROR, "Failed to allocate the bitstring buffer\n");
         return AVERROR(ENOMEM);
     }
     b = *bitstring;

     // P, X, CC
     b[0] = buf[0] & 0x3f;
     // M, PT
     b[1] = buf[1];
     // Timestamp
     b[2] = buf[4];
     b[3] = buf[5];
     b[4] = buf[6];
     b[5] = buf[7];
     /*
      * length_recovery: the unsigned network-ordered sum of lengths of CSRC,
      * padding, extension and media payload
      */
     AV_WB16(b + 6, s->length_recovery);
     // Payload
     memcpy(b + 8, buf + 12, s->length_recovery);

     return 0;
 }

 static int prompeg_write_fec(URLContext *h, PrompegFec *fec, uint8_t type) {
     PrompegContext *s = h->priv_data;
     URLContext *hd;
     uint8_t *buf = s->rtp_buf; // zero-filled
     uint8_t *b = fec->bitstring;
     uint16_t sn;
     int ret;

     sn = type == PROMPEG_FEC_COL ? ++s->rtp_col_sn : ++s->rtp_row_sn;

     // V, P, X, CC
     buf[0] = 0x80 | (b[0] & 0x3f);
     // M, PT
     buf[1] = (b[1] & 0x80) | PROMPEG_RTP_PT;
     // SN
     AV_WB16(buf + 2, sn);
     // TS
     AV_WB32(buf + 4, fec->ts);
     // CSRC=0
     //AV_WB32(buf + 8, 0);
     // SNBase low bits
     AV_WB16(buf + 12, fec->sn);
     // Length recovery
     buf[14] = b[6];
     buf[15] = b[7];
     // E=1, PT recovery
     buf[16] = 0x80 | b[1];
     // Mask=0
     //buf[17] = 0x0;
     //buf[18] = 0x0;
     //buf[19] = 0x0;
     // TS recovery
     buf[20] = b[2];
     buf[21] = b[3];
     buf[22] = b[4];
     buf[23] = b[5];
     // X=0, D, type=0, index=0
     buf[24] = type == PROMPEG_FEC_COL ? 0x0 : 0x40;
     // offset
     buf[25] = type == PROMPEG_FEC_COL ? s->l : 0x1;
     // NA
     buf[26] = type == PROMPEG_FEC_COL ? s->d : s->l;
     // SNBase ext bits=0
     //buf[27] = 0x0;
     // Payload
     memcpy(buf + 28, b + 8, s->length_recovery);

     hd = type == PROMPEG_FEC_COL ? s->fec_col_hd : s->fec_row_hd;
     ret = ffurl_write(hd, buf, s->rtp_buf_size);
     return ret;
 }

 static int prompeg_open(URLContext *h, const char *uri, int flags) {
     PrompegContext *s = h->priv_data;
     AVDictionary *udp_opts = NULL;
     int rtp_port;
     char hostname[256];
     char buf[1024];

     s->fec_col_hd = NULL;
     s->fec_row_hd = NULL;

     if (s->l * s->d > 100) {
         av_log(h, AV_LOG_ERROR, "L * D must be <= 100\n");
         return AVERROR(EINVAL);
     }

     av_url_split(NULL, 0, NULL, 0, hostname, sizeof (hostname), &rtp_port,
             NULL, 0, uri);

     if (rtp_port < 1 || rtp_port > UINT16_MAX - 4) {
         av_log(h, AV_LOG_ERROR, "Invalid RTP base port %d\n", rtp_port);
         return AVERROR(EINVAL);
     }

     if (s->ttl > 0) {
         snprintf(buf, sizeof (buf), "%d", s->ttl);
         av_dict_set(&udp_opts, "ttl", buf, 0);
     }

     ff_url_join(buf, sizeof (buf), "udp", NULL, hostname, rtp_port + 2, NULL);
     if (ffurl_open_whitelist(&s->fec_col_hd, buf, flags, &h->interrupt_callback,
             &udp_opts, h->protocol_whitelist, h->protocol_blacklist, h) < 0)
         goto fail;
     ff_url_join(buf, sizeof (buf), "udp", NULL, hostname, rtp_port + 4, NULL);
     if (ffurl_open_whitelist(&s->fec_row_hd, buf, flags, &h->interrupt_callback,
             &udp_opts, h->protocol_whitelist, h->protocol_blacklist, h) < 0)
         goto fail;

     h->max_packet_size = s->fec_col_hd->max_packet_size;
     s->init = 1;

     av_dict_free(&udp_opts);
     av_log(h, AV_LOG_INFO, "ProMPEG CoP#3-R2 FEC L=%d D=%d\n", s->l, s->d);
     return 0;

 fail:
     ffurl_closep(&s->fec_col_hd);
     ffurl_closep(&s->fec_row_hd);
     av_dict_free(&udp_opts);
     return AVERROR(EIO);
 }

 static int prompeg_init(URLContext *h, const uint8_t *buf, int size) {
     PrompegContext *s = h->priv_data;
     uint32_t seed;
     int i;

     s->fec_arr = NULL;
     s->rtp_buf = NULL;

     if (size < 12 || size > UINT16_MAX + 12) {
         av_log(h, AV_LOG_ERROR, "Invalid RTP packet size\n");
         return AVERROR_INVALIDDATA;
     }

     s->packet_idx = 0;
     s->packet_idx_max = s->l * s->d;
     s->packet_size = size;
     s->length_recovery = size - 12;
     s->rtp_buf_size = 28 + s->length_recovery; // 12 + 16: RTP + FEC headers
     s->bitstring_size = 8 + s->length_recovery; // 8: P, X, CC, M, PT, SN, TS
     s->fec_arr_len = 1 + 2 * s->l; // row + column tmp + column out

     if (h->flags & AVFMT_FLAG_BITEXACT) {
         s->rtp_col_sn = 0;
         s->rtp_row_sn = 0;
     } else {
         seed = av_get_random_seed();
         s->rtp_col_sn = seed & 0x0fff;
         s->rtp_row_sn = (seed >> 16) & 0x0fff;
     }

     s->fec_arr = av_malloc_array(s->fec_arr_len, sizeof (PrompegFec*));
     if (!s->fec_arr) {
         goto fail;
     }
     for (i = 0; i < s->fec_arr_len; i++) {
         s->fec_arr[i] = av_malloc(sizeof (PrompegFec));
         if (!s->fec_arr[i]) {
             goto fail;
         }
         s->fec_arr[i]->bitstring = av_malloc_array(s->bitstring_size, sizeof (uint8_t));
         if (!s->fec_arr[i]->bitstring) {
             av_freep(&s->fec_arr[i]);
             goto fail;
         }
     }
     s->fec_row = *s->fec_arr;
     s->fec_col = s->fec_arr + 1;
     s->fec_col_tmp = s->fec_arr + 1 + s->l;

     s->rtp_buf = av_malloc_array(s->rtp_buf_size, sizeof (uint8_t));
     if (!s->rtp_buf) {
         goto fail;
     }
     memset(s->rtp_buf, 0, s->rtp_buf_size);

     s->init = 0;
     s->first = 1;

     return 0;

 fail:
     av_log(h, AV_LOG_ERROR, "Failed to allocate the FEC buffer\n");
     return AVERROR(ENOMEM);
 }

 static int prompeg_write(URLContext *h, const uint8_t *buf, int size) {
     PrompegContext *s = h->priv_data;
     PrompegFec *fec_tmp;
     uint8_t *bitstring = NULL;
     int col_idx, col_out_idx, row_idx;
     int ret, written = 0;

     if (s->init && ((ret = prompeg_init(h, buf, size)) < 0))
         goto end;

     if ((ret = prompeg_create_bitstring(h, buf, size, &bitstring)) < 0)
         goto end;

     col_idx = s->packet_idx % s->l;
     row_idx = s->packet_idx / s->l % s->d;

     // FEC' (row) send block-aligned, xor
     if (col_idx == 0) {
         if (!s->first || s->packet_idx > 0) {
             if ((ret = prompeg_write_fec(h, s->fec_row, PROMPEG_FEC_ROW)) < 0)
                 goto end;
             written += ret;
         }
         memcpy(s->fec_row->bitstring, bitstring, s->bitstring_size);
         s->fec_row->sn = AV_RB16(buf + 2);
         s->fec_row->ts = AV_RB32(buf + 4);
     } else {
         xor_fast(s->fec_row->bitstring, bitstring, s->fec_row->bitstring,
                 s->bitstring_size);
     }

     // FEC (column) xor
     if (row_idx == 0) {
         if (!s->first) {
             // swap fec_col and fec_col_tmp
             fec_tmp = s->fec_col[col_idx];
             s->fec_col[col_idx] = s->fec_col_tmp[col_idx];
             s->fec_col_tmp[col_idx] = fec_tmp;
         }
         memcpy(s->fec_col_tmp[col_idx]->bitstring, bitstring, s->bitstring_size);
         s->fec_col_tmp[col_idx]->sn = AV_RB16(buf + 2);
         s->fec_col_tmp[col_idx]->ts = AV_RB32(buf + 4);
     } else {
         xor_fast(s->fec_col_tmp[col_idx]->bitstring, bitstring,
                 s->fec_col_tmp[col_idx]->bitstring, s->bitstring_size);
     }

     // FEC (column) send block-aligned
     if (!s->first && s->packet_idx % s->d == 0) {
         col_out_idx = s->packet_idx / s->d;
         if ((ret = prompeg_write_fec(h, s->fec_col[col_out_idx], PROMPEG_FEC_COL)) < 0)
             goto end;
         written += ret;
     }

     if (++s->packet_idx >= s->packet_idx_max) {
         s->packet_idx = 0;
         if (s->first)
             s->first = 0;
     }

     ret = written;

 end:
     av_free(bitstring);
     return ret;
 }

 static int prompeg_close(URLContext *h) {
     PrompegContext *s = h->priv_data;
     int i;

     ffurl_closep(&s->fec_col_hd);
     ffurl_closep(&s->fec_row_hd);

     if (s->fec_arr) {
         for (i = 0; i < s->fec_arr_len; i++) {
             av_free(s->fec_arr[i]->bitstring);
             av_freep(&s->fec_arr[i]);
         }
         av_freep(&s->fec_arr);
     }
     av_freep(&s->rtp_buf);

     return 0;
 }

 const URLProtocol ff_prompeg_protocol = {
     .name                      = "prompeg",
     .url_open                  = prompeg_open,
     .url_write                 = prompeg_write,
     .url_close                 = prompeg_close,
     .priv_data_size            = sizeof(PrompegContext),
     .flags                     = URL_PROTOCOL_FLAG_NETWORK,
     .priv_data_class           = &prompeg_class,
 };
	/*
	* Pro-MPEG Code of Practice #3 Release 2 FEC
	* Copyright (c) 2016 Mobibase, France (http://www.mobibase.com)
	*
	* This file is part of FFmpeg.
	*
	* FFmpeg is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* FFmpeg is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with FFmpeg; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	/**
	* @file
	* Pro-MPEG Code of Practice #3 Release 2 FEC protocol
	* @author Vlad Tarca <vlad.tarca@gmail.com>
	*/

	/*
	* Reminder:

	[RFC 2733] FEC Packet Structure

	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| RTP Header \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| FEC Header \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| FEC Payload \|
	\| \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


	[RFC 3550] RTP header

	0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\|V=2\|P\|X\| CC \|M\| PT \| sequence number \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| timestamp \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| synchronization source (SSRC) identifier \|
	+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
	\| contributing source (CSRC) identifiers \|
	\| .... \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	[RFC 3550] RTP header extension (after CSRC)

	0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| defined by profile \| length \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| header extension \|
	\| .... \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	[Pro-MPEG COP3] FEC Header

	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| SNBase low bits \| length recovery \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\|E\| PT recovery \| mask \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\| TS recovery \|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	\|X\|D\|type \|index\| offset \| NA \|SNBase ext bits\|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

	*/

	#include "libavutil/avstring.h"
	#include "libavutil/intreadwrite.h"
	#include "libavutil/opt.h"
	#include "libavutil/parseutils.h"
	#include "libavutil/random_seed.h"
	#include "avformat.h"
	#include "config.h"
	#include "url.h"

	#define PROMPEG_RTP_PT 0x60
	#define PROMPEG_FEC_COL 0x0
	#define PROMPEG_FEC_ROW 0x1

	typedef struct PrompegFec {
	uint16_t sn;
	uint32_t ts;
	uint8_t *bitstring;
	} PrompegFec;

	typedef struct PrompegContext {
	const AVClass *class;
	URLContext fec_col_hd, fec_row_hd;
	PrompegFec fec_arr, fec_col_tmp, *fec_col, fec_row;
	int ttl;
	uint8_t l, d;
	uint8_t *rtp_buf;
	uint16_t rtp_col_sn, rtp_row_sn;
	uint16_t length_recovery;
	int packet_size;
	int packet_idx, packet_idx_max;
	int fec_arr_len;
	int bitstring_size;
	int rtp_buf_size;
	int init;
	int first;
	} PrompegContext;

	#define OFFSET(x) offsetof(PrompegContext, x)
	#define E AV_OPT_FLAG_ENCODING_PARAM

	static const AVOption options[] = {
	{ "ttl", "Time to live (in milliseconds, multicast only)", OFFSET(ttl), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, INT_MAX, .flags = E },
	{ "l", "FEC L", OFFSET(l), AV_OPT_TYPE_INT, { .i64 = 5 }, 4, 20, .flags = E },
	{ "d", "FEC D", OFFSET(d), AV_OPT_TYPE_INT, { .i64 = 5 }, 4, 20, .flags = E },
	{ NULL }
	};

	static const AVClass prompeg_class = {
	.class_name = "prompeg",
	.item_name = av_default_item_name,
	.option = options,
	.version = LIBAVUTIL_VERSION_INT,
	};

	static void xor_fast(const uint8_t in1, const uint8_t in2, uint8_t *out, int size) {
	int i, n, s;

	#if HAVE_FAST_64BIT
	uint64_t v1, v2;

	n = size / sizeof (uint64_t);
	s = n * sizeof (uint64_t);

	for (i = 0; i < n; i++) {
	v1 = AV_RN64A(in1);
	v2 = AV_RN64A(in2);
	AV_WN64A(out, v1 ^ v2);
	in1 += 8;
	in2 += 8;
	out += 8;
	}
	#else
	uint32_t v1, v2;

	n = size / sizeof (uint32_t);
	s = n * sizeof (uint32_t);

	for (i = 0; i < n; i++) {
	v1 = AV_RN32A(in1);
	v2 = AV_RN32A(in2);
	AV_WN32A(out, v1 ^ v2);
	in1 += 4;
	in2 += 4;
	out += 4;
	}
	#endif

	n = size - s;

	for (i = 0; i < n; i++) {
	out[i] = in1[i] ^ in2[i];
	}
	}

	static int prompeg_create_bitstring(URLContext h, const uint8_t buf, int size,
	uint8_t **bitstring) {
	PrompegContext *s = h->priv_data;
	uint8_t *b;

	if (size < 12 \|\| (buf[0] & 0xc0) != 0x80 \|\| (buf[1] & 0x7f) != 0x21) {
	av_log(h, AV_LOG_ERROR, "Unsupported stream format (expected MPEG-TS over RTP)\n");
	return AVERROR(EINVAL);
	}
	if (size != s->packet_size) {
	av_log(h, AV_LOG_ERROR, "The RTP packet size must be constant (set pkt_size)\n");
	return AVERROR(EINVAL);
	}

	*bitstring = av_malloc(s->bitstring_size);
	if (!*bitstring) {
	av_log(h, AV_LOG_ERROR, "Failed to allocate the bitstring buffer\n");
	return AVERROR(ENOMEM);
	}
	b = *bitstring;

	// P, X, CC
	b[0] = buf[0] & 0x3f;
	// M, PT
	b[1] = buf[1];
	// Timestamp
	b[2] = buf[4];
	b[3] = buf[5];
	b[4] = buf[6];
	b[5] = buf[7];
	/*
	* length_recovery: the unsigned network-ordered sum of lengths of CSRC,
	* padding, extension and media payload
	*/
	AV_WB16(b + 6, s->length_recovery);
	// Payload
	memcpy(b + 8, buf + 12, s->length_recovery);

	return 0;
	}

	static int prompeg_write_fec(URLContext h, PrompegFec fec, uint8_t type) {
	PrompegContext *s = h->priv_data;
	URLContext *hd;
	uint8_t *buf = s->rtp_buf; // zero-filled
	uint8_t *b = fec->bitstring;
	uint16_t sn;
	int ret;

	sn = type == PROMPEG_FEC_COL ? ++s->rtp_col_sn : ++s->rtp_row_sn;

	// V, P, X, CC
	buf[0] = 0x80 \| (b[0] & 0x3f);
	// M, PT
	buf[1] = (b[1] & 0x80) \| PROMPEG_RTP_PT;
	// SN
	AV_WB16(buf + 2, sn);
	// TS
	AV_WB32(buf + 4, fec->ts);
	// CSRC=0
	//AV_WB32(buf + 8, 0);
	// SNBase low bits
	AV_WB16(buf + 12, fec->sn);
	// Length recovery
	buf[14] = b[6];
	buf[15] = b[7];
	// E=1, PT recovery
	buf[16] = 0x80 \| b[1];
	// Mask=0
	//buf[17] = 0x0;
	//buf[18] = 0x0;
	//buf[19] = 0x0;
	// TS recovery
	buf[20] = b[2];
	buf[21] = b[3];
	buf[22] = b[4];
	buf[23] = b[5];
	// X=0, D, type=0, index=0
	buf[24] = type == PROMPEG_FEC_COL ? 0x0 : 0x40;
	// offset
	buf[25] = type == PROMPEG_FEC_COL ? s->l : 0x1;
	// NA
	buf[26] = type == PROMPEG_FEC_COL ? s->d : s->l;
	// SNBase ext bits=0
	//buf[27] = 0x0;
	// Payload
	memcpy(buf + 28, b + 8, s->length_recovery);

	hd = type == PROMPEG_FEC_COL ? s->fec_col_hd : s->fec_row_hd;
	ret = ffurl_write(hd, buf, s->rtp_buf_size);
	return ret;
	}

	static int prompeg_open(URLContext h, const char uri, int flags) {
	PrompegContext *s = h->priv_data;
	AVDictionary *udp_opts = NULL;
	int rtp_port;
	char hostname[256];
	char buf[1024];

	s->fec_col_hd = NULL;
	s->fec_row_hd = NULL;

	if (s->l * s->d > 100) {
	av_log(h, AV_LOG_ERROR, "L * D must be <= 100\n");
	return AVERROR(EINVAL);
	}

	av_url_split(NULL, 0, NULL, 0, hostname, sizeof (hostname), &rtp_port,
	NULL, 0, uri);

	if (rtp_port < 1 \|\| rtp_port > UINT16_MAX - 4) {
	av_log(h, AV_LOG_ERROR, "Invalid RTP base port %d\n", rtp_port);
	return AVERROR(EINVAL);
	}

	if (s->ttl > 0) {
	snprintf(buf, sizeof (buf), "%d", s->ttl);
	av_dict_set(&udp_opts, "ttl", buf, 0);
	}

	ff_url_join(buf, sizeof (buf), "udp", NULL, hostname, rtp_port + 2, NULL);
	if (ffurl_open_whitelist(&s->fec_col_hd, buf, flags, &h->interrupt_callback,
	&udp_opts, h->protocol_whitelist, h->protocol_blacklist, h) < 0)
	goto fail;
	ff_url_join(buf, sizeof (buf), "udp", NULL, hostname, rtp_port + 4, NULL);
	if (ffurl_open_whitelist(&s->fec_row_hd, buf, flags, &h->interrupt_callback,
	&udp_opts, h->protocol_whitelist, h->protocol_blacklist, h) < 0)
	goto fail;

	h->max_packet_size = s->fec_col_hd->max_packet_size;
	s->init = 1;

	av_dict_free(&udp_opts);
	av_log(h, AV_LOG_INFO, "ProMPEG CoP#3-R2 FEC L=%d D=%d\n", s->l, s->d);
	return 0;

	fail:
	ffurl_closep(&s->fec_col_hd);
	ffurl_closep(&s->fec_row_hd);
	av_dict_free(&udp_opts);
	return AVERROR(EIO);
	}

	static int prompeg_init(URLContext h, const uint8_t buf, int size) {
	PrompegContext *s = h->priv_data;
	uint32_t seed;
	int i;

	s->fec_arr = NULL;
	s->rtp_buf = NULL;

	if (size < 12 \|\| size > UINT16_MAX + 12) {
	av_log(h, AV_LOG_ERROR, "Invalid RTP packet size\n");
	return AVERROR_INVALIDDATA;
	}

	s->packet_idx = 0;
	s->packet_idx_max = s->l * s->d;
	s->packet_size = size;
	s->length_recovery = size - 12;
	s->rtp_buf_size = 28 + s->length_recovery; // 12 + 16: RTP + FEC headers
	s->bitstring_size = 8 + s->length_recovery; // 8: P, X, CC, M, PT, SN, TS
	s->fec_arr_len = 1 + 2 * s->l; // row + column tmp + column out

	if (h->flags & AVFMT_FLAG_BITEXACT) {
	s->rtp_col_sn = 0;
	s->rtp_row_sn = 0;
	} else {
	seed = av_get_random_seed();
	s->rtp_col_sn = seed & 0x0fff;
	s->rtp_row_sn = (seed >> 16) & 0x0fff;
	}

	s->fec_arr = av_malloc_array(s->fec_arr_len, sizeof (PrompegFec*));
	if (!s->fec_arr) {
	goto fail;
	}
	for (i = 0; i < s->fec_arr_len; i++) {
	s->fec_arr[i] = av_malloc(sizeof (PrompegFec));
	if (!s->fec_arr[i]) {
	goto fail;
	}
	s->fec_arr[i]->bitstring = av_malloc_array(s->bitstring_size, sizeof (uint8_t));
	if (!s->fec_arr[i]->bitstring) {
	av_freep(&s->fec_arr[i]);
	goto fail;
	}
	}
	s->fec_row = *s->fec_arr;
	s->fec_col = s->fec_arr + 1;
	s->fec_col_tmp = s->fec_arr + 1 + s->l;

	s->rtp_buf = av_malloc_array(s->rtp_buf_size, sizeof (uint8_t));
	if (!s->rtp_buf) {
	goto fail;
	}
	memset(s->rtp_buf, 0, s->rtp_buf_size);

	s->init = 0;
	s->first = 1;

	return 0;

	fail:
	av_log(h, AV_LOG_ERROR, "Failed to allocate the FEC buffer\n");
	return AVERROR(ENOMEM);
	}

	static int prompeg_write(URLContext h, const uint8_t buf, int size) {
	PrompegContext *s = h->priv_data;
	PrompegFec *fec_tmp;
	uint8_t *bitstring = NULL;
	int col_idx, col_out_idx, row_idx;
	int ret, written = 0;

	if (s->init && ((ret = prompeg_init(h, buf, size)) < 0))
	goto end;

	if ((ret = prompeg_create_bitstring(h, buf, size, &bitstring)) < 0)
	goto end;

	col_idx = s->packet_idx % s->l;
	row_idx = s->packet_idx / s->l % s->d;

	// FEC' (row) send block-aligned, xor
	if (col_idx == 0) {
	if (!s->first \|\| s->packet_idx > 0) {
	if ((ret = prompeg_write_fec(h, s->fec_row, PROMPEG_FEC_ROW)) < 0)
	goto end;
	written += ret;
	}
	memcpy(s->fec_row->bitstring, bitstring, s->bitstring_size);
	s->fec_row->sn = AV_RB16(buf + 2);
	s->fec_row->ts = AV_RB32(buf + 4);
	} else {
	xor_fast(s->fec_row->bitstring, bitstring, s->fec_row->bitstring,
	s->bitstring_size);
	}

	// FEC (column) xor
	if (row_idx == 0) {
	if (!s->first) {
	// swap fec_col and fec_col_tmp
	fec_tmp = s->fec_col[col_idx];
	s->fec_col[col_idx] = s->fec_col_tmp[col_idx];
	s->fec_col_tmp[col_idx] = fec_tmp;
	}
	memcpy(s->fec_col_tmp[col_idx]->bitstring, bitstring, s->bitstring_size);
	s->fec_col_tmp[col_idx]->sn = AV_RB16(buf + 2);
	s->fec_col_tmp[col_idx]->ts = AV_RB32(buf + 4);
	} else {
	xor_fast(s->fec_col_tmp[col_idx]->bitstring, bitstring,
	s->fec_col_tmp[col_idx]->bitstring, s->bitstring_size);
	}

	// FEC (column) send block-aligned
	if (!s->first && s->packet_idx % s->d == 0) {
	col_out_idx = s->packet_idx / s->d;
	if ((ret = prompeg_write_fec(h, s->fec_col[col_out_idx], PROMPEG_FEC_COL)) < 0)
	goto end;
	written += ret;
	}

	if (++s->packet_idx >= s->packet_idx_max) {
	s->packet_idx = 0;
	if (s->first)
	s->first = 0;
	}

	ret = written;

	end:
	av_free(bitstring);
	return ret;
	}

	static int prompeg_close(URLContext *h) {
	PrompegContext *s = h->priv_data;
	int i;

	ffurl_closep(&s->fec_col_hd);
	ffurl_closep(&s->fec_row_hd);

	if (s->fec_arr) {
	for (i = 0; i < s->fec_arr_len; i++) {
	av_free(s->fec_arr[i]->bitstring);
	av_freep(&s->fec_arr[i]);
	}
	av_freep(&s->fec_arr);
	}
	av_freep(&s->rtp_buf);

	return 0;
	}

	const URLProtocol ff_prompeg_protocol = {
	.name = "prompeg",
	.url_open = prompeg_open,
	.url_write = prompeg_write,
	.url_close = prompeg_close,
	.priv_data_size = sizeof(PrompegContext),
	.flags = URL_PROTOCOL_FLAG_NETWORK,
	.priv_data_class = &prompeg_class,
	};