[FFmpeg-devel] [PATCH] Add optional NIT table generation
Marton Balint
cus at passwd.hu
Sun May 2 23:11:16 EEST 2021
On Tue, 27 Apr 2021, Ubaldo Porcheddu wrote:
> Signed-off-by: Ubaldo Porcheddu <ubaldo at eja.it>
> ---
> libavformat/mpegtsenc.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 106 insertions(+), 4 deletions(-)
>
> diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
> index a357f3a6aa..d03eaaa009 100644
> --- a/libavformat/mpegtsenc.c
> +++ b/libavformat/mpegtsenc.c
> @@ -76,10 +76,12 @@ typedef struct MpegTSWrite {
> const AVClass *av_class;
> MpegTSSection pat; /* MPEG-2 PAT table */
> MpegTSSection sdt; /* MPEG-2 SDT table context */
> + MpegTSSection nit; /* MPEG-2 NIT table context */
> MpegTSService **services;
> AVPacket *pkt;
> int64_t sdt_period; /* SDT period in PCR time base */
> int64_t pat_period; /* PAT/PMT period in PCR time base */
> + int64_t nit_period; /* NIT period in PCR time base */
> int nb_services;
> int64_t first_pcr;
> int first_dts_checked;
> @@ -112,10 +114,13 @@ typedef struct MpegTSWrite {
> int tables_version;
> int64_t pat_period_us;
> int64_t sdt_period_us;
> + int64_t nit_period_us;
> int64_t last_pat_ts;
> int64_t last_sdt_ts;
> + int64_t last_nit_ts;
>
> int omit_video_pes_length;
> + int nit_enable;
Instead of this, you should add a new MPEGTS_FLAG.
> } MpegTSWrite;
>
> /* a PES packet header is generated every DEFAULT_PES_HEADER_FREQ packets */
> @@ -227,6 +232,7 @@ static int mpegts_write_section1(MpegTSSection *s, int tid, int id,
> #define SDT_RETRANS_TIME 500
> #define PAT_RETRANS_TIME 100
> #define PCR_RETRANS_TIME 20
> +#define NIT_RETRANS_TIME 500
>
> typedef struct MpegTSWriteStream {
> int pid; /* stream associated pid */
> @@ -796,6 +802,75 @@ static void mpegts_write_sdt(AVFormatContext *s)
> data, q - data);
> }
>
> +static void mpegts_write_nit(AVFormatContext *s)
> +{
> + int i, len=0, provider_len=0, desc_len=0, virtual_channel_value;
> + MpegTSWrite *ts = s->priv_data;
> + uint8_t data[SECTION_LENGTH], *q, *desc_len_ptr, *loop_len_ptr;
> + AVDictionaryEntry *provider, *virtual_channel;
> + AVProgram *program;
> + const char *provider_name;
> +
> + q = data;
> +
> + //network name
> + provider = av_dict_get(s->metadata, "service_provider", NULL, 0);
> + provider_name = provider ? provider->value : DEFAULT_PROVIDER_NAME;
> + provider_len = strlen(provider_name);
> + put16(&q, 0xf000 | provider_len);
> + *q++ = 0x40;
> + *q++ = provider_len;
> + putbuf(&q, provider_name, provider_len);
encode_str8 should be used instead. Better yet, you should pre-calculate
that at init time, and used the already encoded value here directly.
> +
> + //TS loop
> + loop_len_ptr = q;
> + q += 2;
> + put16(&q, ts->transport_stream_id);
> + put16(&q, ts->original_network_id);
> +
> + //transport descriptor
> + desc_len_ptr = q;
> + q += 2;
> +
> + //service list
> + len = 3 * ts->nb_services;
> + desc_len += len;
> + *q++ = 0x41; //tag
> + *q++ = len;
> + for(i = 0; i < ts->nb_services; i++) {
> + put16(&q, ts->services[i]->sid);//service_ID
> + *q++ = 0x01; //service type 0x01 for Digital TV Service
ts->service_type
Preferably you should use 4 space indentation.
> + }
> +
> + //private data
> + desc_len += 6 + 2;
> + *q++ = 0x5F;
> + *q++ = 4;
> + *q++ = 0x00;
> + *q++ = 0x00;
> + put16(&q, 40);
What are these?
> +
> + //virtual channel
> + len = 4 * ts->nb_services;
> + desc_len += len + 2;
> + *q++ = 0x83;
> + *q++ = len;
Simply *q++ = 4 * ts->nb_services
> + for (i = 0; i < ts->nb_services; i++) {
> + program = s->programs[i];
> + virtual_channel = av_dict_get(program->metadata, "virtual_channel", NULL, 0);
> + virtual_channel_value = virtual_channel ? atoi(virtual_channel->value) : 1000+i;
> + put16(&q, ts->services[i]->sid);
> + put16(&q, 0xfc00 | virtual_channel_value);
indentation
> + }
> +
> + //calculate lengths
> + put16(&desc_len_ptr, 0xf000 | desc_len);
> + put16(&loop_len_ptr, 0xf000 | desc_len+6);
You should not calculate desc_len, you should use
(q - desc_len_ptr) directly, it is less error-prone that way.
> +
> + mpegts_write_section1(&ts->nit, NIT_TID, ts->original_network_id, ts->tables_version, 0, 0,
> + data, q - data);
> +}
> +
> /* This stores a string in buf with the correct encoding and also sets the
> * first byte as the length. !str is accepted for an empty string.
> * If the string is already encoded, invalid UTF-8 or has no multibyte sequence
> @@ -1022,6 +1097,12 @@ static int mpegts_init(AVFormatContext *s)
> ts->sdt.write_packet = section_write_packet;
> ts->sdt.opaque = s;
>
> + ts->nit.pid = NIT_PID;
> + ts->nit.cc = 15;
> + ts->nit.discontinuity= ts->flags & MPEGTS_FLAG_DISCONT;
> + ts->nit.write_packet = section_write_packet;
> + ts->nit.opaque = s;
> +
> ts->pkt = av_packet_alloc();
> if (!ts->pkt)
> return AVERROR(ENOMEM);
> @@ -1143,8 +1224,10 @@ static int mpegts_init(AVFormatContext *s)
>
> ts->last_pat_ts = AV_NOPTS_VALUE;
> ts->last_sdt_ts = AV_NOPTS_VALUE;
> + ts->last_nit_ts = AV_NOPTS_VALUE;
> ts->pat_period = av_rescale(ts->pat_period_us, PCR_TIME_BASE, AV_TIME_BASE);
> ts->sdt_period = av_rescale(ts->sdt_period_us, PCR_TIME_BASE, AV_TIME_BASE);
> + ts->nit_period = av_rescale(ts->nit_period_us, PCR_TIME_BASE, AV_TIME_BASE);
>
> if (ts->mux_rate == 1)
> av_log(s, AV_LOG_VERBOSE, "muxrate VBR, ");
> @@ -1154,12 +1237,14 @@ static int mpegts_init(AVFormatContext *s)
> "sdt every %"PRId64" ms, pat/pmt every %"PRId64" ms\n",
> av_rescale(ts->sdt_period, 1000, PCR_TIME_BASE),
> av_rescale(ts->pat_period, 1000, PCR_TIME_BASE));
> + if (ts->nit_enable > 0)
> + av_log(s, AV_LOG_VERBOSE, "nit every %"PRId64" ms\n", av_rescale(ts->nit_period, 1000, PCR_TIME_BASE));
Maybe you should continue the last log line which already describes the
interval of various tables, and not start a new line.
>
> return 0;
> }
>
> -/* send SDT, PAT and PMT tables regularly */
> -static void retransmit_si_info(AVFormatContext *s, int force_pat, int force_sdt, int64_t pcr)
> +/* send SDT, NIT, PAT and PMT tables regularly */
> +static void retransmit_si_info(AVFormatContext *s, int force_pat, int force_sdt, int force_nit, int64_t pcr)
> {
> MpegTSWrite *ts = s->priv_data;
> int i;
> @@ -1172,6 +1257,16 @@ static void retransmit_si_info(AVFormatContext *s, int force_pat, int force_sdt,
> ts->last_sdt_ts = FFMAX(pcr, ts->last_sdt_ts);
> mpegts_write_sdt(s);
> }
> + if ((pcr != AV_NOPTS_VALUE && ts->last_nit_ts == AV_NOPTS_VALUE) ||
> + (pcr != AV_NOPTS_VALUE && pcr - ts->last_nit_ts >= ts->nit_period) ||
> + force_nit
> + ) {
> + if (pcr != AV_NOPTS_VALUE)
> + ts->last_nit_ts = FFMAX(pcr, ts->last_nit_ts);
> + if (ts->nit_enable > 0) {
> + mpegts_write_nit(s);
> + }
> + }
indentation
> if ((pcr != AV_NOPTS_VALUE && ts->last_pat_ts == AV_NOPTS_VALUE) ||
> (pcr != AV_NOPTS_VALUE && pcr - ts->last_pat_ts >= ts->pat_period) ||
> force_pat) {
> @@ -1305,6 +1400,7 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
> int64_t delay = av_rescale(s->max_delay, 90000, AV_TIME_BASE);
> int force_pat = st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && key && !ts_st->prev_payload_key;
> int force_sdt = 0;
> + int force_nit = 0;
>
> av_assert0(ts_st->payload != buf || st->codecpar->codec_type != AVMEDIA_TYPE_VIDEO);
> if (ts->flags & MPEGTS_FLAG_PAT_PMT_AT_FRAMES && st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
> @@ -1314,6 +1410,7 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
> if (ts->flags & MPEGTS_FLAG_REEMIT_PAT_PMT) {
> force_pat = 1;
> force_sdt = 1;
> + force_nit = 1;
> ts->flags &= ~MPEGTS_FLAG_REEMIT_PAT_PMT;
> }
>
> @@ -1325,9 +1422,10 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
> else if (dts != AV_NOPTS_VALUE)
> pcr = (dts - delay) * 300;
>
> - retransmit_si_info(s, force_pat, force_sdt, pcr);
> + retransmit_si_info(s, force_pat, force_sdt, force_nit, pcr);
> force_pat = 0;
> force_sdt = 0;
> + force_nit = 0;
>
> write_pcr = 0;
> if (ts->mux_rate > 1) {
> @@ -2115,7 +2213,7 @@ static const AVOption options[] = {
> { "initial_discontinuity", "Mark initial packets as discontinuous",
> 0, AV_OPT_TYPE_CONST, { .i64 = MPEGTS_FLAG_DISCONT }, 0, INT_MAX, ENC, "mpegts_flags" },
> { "mpegts_copyts", "don't offset dts/pts", OFFSET(copyts), AV_OPT_TYPE_BOOL, { .i64 = -1 }, -1, 1, ENC },
> - { "tables_version", "set PAT, PMT and SDT version", OFFSET(tables_version), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 31, ENC },
> + { "tables_version", "set PAT, PMT, SDT and NIT version", OFFSET(tables_version), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 31, ENC },
> { "omit_video_pes_length", "Omit the PES packet length for video packets",
> OFFSET(omit_video_pes_length), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, ENC },
> { "pcr_period", "PCR retransmission time in milliseconds",
> @@ -2124,6 +2222,10 @@ static const AVOption options[] = {
> OFFSET(pat_period_us), AV_OPT_TYPE_DURATION, { .i64 = PAT_RETRANS_TIME * 1000LL }, 0, INT64_MAX, ENC },
> { "sdt_period", "SDT retransmission time limit in seconds",
> OFFSET(sdt_period_us), AV_OPT_TYPE_DURATION, { .i64 = SDT_RETRANS_TIME * 1000LL }, 0, INT64_MAX, ENC },
> + { "nit_period", "NIT retransmission time limit in seconds",
> + OFFSET(nit_period_us), AV_OPT_TYPE_DURATION, { .i64 = NIT_RETRANS_TIME * 1000LL }, 0, INT64_MAX, ENC },
> + { "nit_enable", "Enable NIT transmission",
> + OFFSET(nit_enable), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, ENC },
As I wrote earlier, instead of a separate option, you should introduce a
new flag in mpegts_flags.
Also docs/muxers.texi update is missing for the new feature.
Regards,
Marton
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