Shulou(Shulou.com)06/03 Report--

+-+ | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |

| | FU indicator |

< == >

+-+ +

+-+ | F | NRI | Type |

+-+

+-+

+-+ | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |

| | FU header |

< == >

+-+ +

+-+ | S | E | R | Type |

+-+

-

/ / return 0 on packet, no more left, 1 on packet, 1 on partial packet

Static int h364_handle_packet (AVFormatContext * ctx, PayloadContext * data

AVStream * st, AVPacket * pkt, uint32_t * timestamp

Const uint8_t * buf, int len, uint16_t seq

Int flags)

{

Uint8_t nal

Uint8_t type

Int result = 0

If (! len) {

Av_log (ctx, AV_LOG_ERROR, "Empty H.264 RTP packet\ n")

Return AVERROR_INVALIDDATA

}

Nal = buf [0]; / / the first byte is FU indicator

Type = nal & 0x1f / take the next five bytes

/ * Simplify the case (these are all the NAL types used internally by

* the H.264 codec). , /

If (type > = 1 & & type data, start_sequence, sizeof (start_sequence))

Memcpy (pkt- > data + sizeof (start_sequence), buf, len)

COUNT_NAL_TYPE (data, nal)

Break

Case 24: / / STAP-A (one packet, multiple nals)

/ / consume the STAP-A NAL

Buf++

Len--

Result = ff_h364_handle_aggregated_packet (ctx, data, pkt, buf, len, 0

NAL_COUNTERS, NAL_MASK)

Break

Case 25: / / STAP-B

Case 26: / / MTAP-16

Case 27: / / MTAP-24

Case 29: / / FU-B

Avpriv_report_missing_feature (ctx, "RTP H.264 NAL unit type d", type)

Result = AVERROR_PATCHWELCOME

Break

Case 28: / / FU-A (fragmented nal)

Result = h364_handle_packet_fu_a (ctx, data, pkt, buf, len

NAL_COUNTERS, NAL_MASK)

Break

Case 30: / / undefined

Case 31: / / undefined

Default:

Av_log (ctx, AV_LOG_ERROR, "Undefined type (% d)\ n", type)

Result = AVERROR_INVALIDDATA

Break

}

Pkt- > stream_index = st- > index

Return result

}

Static int h364_handle_packet_fu_a (AVFormatContext * ctx, PayloadContext * data, AVPacket * pkt

Const uint8_t * buf, int len

Int * nal_counters, int nal_mask)

{

Uint8_t fu_indicator, fu_header, start_bit, nal_type, nal

If (len

< 3) { av_log(ctx, AV_LOG_ERROR, "Too short data for FU-A H.264 RTP packet\n"); return AVERROR_INVALIDDATA; } fu_indicator = buf[0]; fu_header = buf[1]; start_bit = fu_header >

> 7

Nal_type = fu_header & 0x1f

Nal = fu_indicator & 0xe0 | nal_type

/ / skip the fu_indicator and fu_header

Buf + = 2

Len-= 2

If (start_bit & & nal_counters)

Nal_ counters [nal _ type & nal_mask] + +

Return ff_h364_handle_frag_packet (pkt, buf, len, start_bit, & nal, 1)

}

FU identifier

0... .... = F bit: No bit errors or other syntax violations

.10. .... = Nal_ref_idc (NRI): 2

... 1 1100 = Type: Fragmentation unit A (FU-A) (28)

FU Header

1... .... = Start bit: the first packet of FU-A picture

.0.. .... = End bit: Not the last packet of FU-A picture

.. 0. .... = Forbidden bit: 0

... 0 0001 = Nal_unit_type: Coded slice of a non-IDR picture (1)

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