November 2006 - NUT-devel - lists.mplayerhq.hu

Fourcc spec
by Oded Shimon 31 May '07

31 May '07

This specification is normative to demuxers, informative to muxers. It does not need to be actively maintained, because it does NOT list all legal fourcc's, only the ones noted by the specification. I'd like to commit it to nut/docs/fourcc.txt . - ods15

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possible error in the spec for the index
by Michael Niedermayer 23 Dec '06

23 Dec '06

Hi when trying to read the index from a libnut generated file i stumbled across a odd problem in how the index is stored, the problem is that from nut.txt: has_keyframe indicates whether this stream has a keyframe between this syncpoint and the last syncpoint. what is "this syncpoint", libnut seems to use syncpoint[0] for has_keyframe[0] as "this" but with that definition has_keyframe[0]=0 (which is harmless) more problematic is for(; j<n && j<syncpoints; j++){ a keyframe after the last syncpoint would be has_keyframe[syncpoints] and so the pts/eor loop wouldnt be run on it -> we would know there is a keyframe but we dont not know its pts obvious solutions (assuiming i didnt miss something) 1. ignore it, its just one keyframe per stream which isnt in the index 2. redefine has_keyframe so [0] is for sp[0] ... sp[1] 3. change j<syncpoints to j<syncpoints+1 comments? -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In the past you could go to a library and read, borrow or copy any book Today you'd get arrested for mere telling someone where the library is

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r21405 - trunk/DOCS/tech/nut.txt
by ivo 30 Nov '06

30 Nov '06

Author: ivo Date: Thu Nov 30 22:59:55 2006 New Revision: 21405 Modified: trunk/DOCS/tech/nut.txt Log: move reserved_bytes out of packet_footer. this makes all packets uniform. Modified: trunk/DOCS/tech/nut.txt ============================================================================== --- trunk/DOCS/tech/nut.txt (original) +++ trunk/DOCS/tech/nut.txt Thu Nov 30 22:59:55 2006 @@ -215,9 +215,7 @@ header_checksum u(32) packet_footer - reserved_bytes checksum u(32) - [Note: in index packet, reserved_bytes comes before index_ptr] reserved_headers while(next_byte == 'N' && next_code != main_startcode @@ -226,6 +224,7 @@ && next_code != index_startcode && next_code != syncpoint_startcode){ packet_header + reserved_bytes packet_footer } @@ -272,6 +271,7 @@ reserved_count[i]= tmp_res; } } + reserved_bytes stream_header: stream_id v @@ -294,6 +294,7 @@ samplerate_denom v channel_count v } + reserved_bytes Basic Packets: @@ -394,10 +395,12 @@ type= "v" } } + reserved_bytes syncpoint: global_key_pts t back_ptr_div16 v + reserved_bytes Complete definition:

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reserved bytes
by Ivo 28 Nov '06

28 Nov '06

Hi, I stumbled upon the following: packet_footer reserved_bytes checksum u(32) [Note: in index packet, reserved_bytes comes before index_ptr] Wouldn't it be cleaner and easier to understand to just move reserved_bytes to the end of each header? Like: packet_header .... some_header (!=index) .... reserved_bytes packet_footer checksum u(32) and packet_header .... index .... reserved_bytes index_ptr f(64) packet_footer checksum u(32) This removes the need for the [Note:...]-exception for index packets and should result in the same bitstream as before. --Ivo

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a few things about nut.txt
by Ivo 27 Nov '06

27 Nov '06

Hi, While reading the spec, I noticed a few things that could improve readability IMHO: 1.) It would be handy to have the type mentioned after each tag in the tag description section. It is tiresome to have to scroll back each time. e.g. chapter_id (s) stream_class (v) fourcc (vb) et cetera 2.) The first column of the frame_flags table is called Bit, but there is no such thing as the 4096th bit of a 64-bit value. I suggest changing the column-heading to Mask or change the column-entries to represent the bit number (i.e. 0, 1, 3, 4, 5, 6, 7, 12, 13). 3.) There is no explanation of what EOR actually means. I could change 1.) and 2.) if nobody objects. For 3.) I need an explanation first :-) --Ivo

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r21294 - trunk/DOCS/tech/nut.txt
by ivo 26 Nov '06

26 Nov '06

Author: ivo Date: Sun Nov 26 23:50:47 2006 New Revision: 21294 Modified: trunk/DOCS/tech/nut.txt Log: rename all *_nom (nominator) to the correct *_num (numerator) Modified: trunk/DOCS/tech/nut.txt ============================================================================== --- trunk/DOCS/tech/nut.txt (original) +++ trunk/DOCS/tech/nut.txt Sun Nov 26 23:50:47 2006 @@ -237,9 +237,9 @@ max_distance v time_base_count v for(i=0; i<time_base_count; i++) - time_base_nom v + time_base_num v time_base_denom v - time_base[i]= time_base_nom/time_base_denom + time_base[i]= time_base_num/time_base_denom tmp_pts=0 tmp_mul=1 tmp_stream=0 @@ -290,7 +290,7 @@ sample_height v colorspace_type v }else if(stream_class == audio){ - samplerate_nom v + samplerate_num v samplerate_denom v channel_count v } @@ -495,14 +495,14 @@ the id values used are the same as in avi, so if a codec uses a specific fourcc in avi then the same fourcc MUST be used here -time_base_nom (v) / time_base_denom (v) = time_base +time_base_num (v) / time_base_denom (v) = time_base the length of a timer tick in seconds, this MUST be equal to the 1/fps if FLAG_FIXED_FPS is set - time_base_nom and time_base_denom MUST NOT be 0 - time_base_nom and time_base_denom MUST be relatively prime + time_base_num and time_base_denom MUST NOT be 0 + time_base_num and time_base_denom MUST be relatively prime time_base_denom MUST be < 2^31 examples: - fps time_base_nom time_base_denom + fps time_base_num time_base_denom 30 1 30 29.97 1001 30000 23.976 1001 24000 @@ -517,10 +517,10 @@ To switch from 2 different timebases, the following calculation is defined: - ln = from_time_base_nom*to_time_base_denom + ln = from_time_base_num*to_time_base_denom sn = from_timestamp d1 = from_time_base_denom - d2 = to_time_base_nom + d2 = to_time_base_num timestamp = (ln/d1*sn + ln%d1*sn/d1)/d2 Note: this calculation MUST be done with unsigned 64 bit integers, and is equivalent to (ln*sn)/(d1*d2) but this would require a 96bit integer @@ -711,7 +711,7 @@ 17 ITU Rec 624 / ITU Rec 601 Y range: 0..255 Cb/Cr range: 0..255 18 ITU Rec 709 Y range: 0..255 Cb/Cr range: 0..255 -samplerate_nom (v) / samplerate_denom (v) = samplerate +samplerate_num (v) / samplerate_denom (v) = samplerate the number of samples per second, MUST NOT be 0 crc32 checksum

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typo?
by Ivo 26 Nov '06

26 Nov '06

Hi, In the description of an info packet, I found the following: .... }else if (value<-4){ type= "r" value.den= -value-4 value.num s }else{ .... I suppose that should be "value.nom" ? --Ivo

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r21211 - trunk/DOCS/tech/nut.txt
by michael 25 Nov '06

25 Nov '06

Author: michael Date: Sat Nov 25 12:28:38 2006 New Revision: 21211 Modified: trunk/DOCS/tech/nut.txt Log: a few more clarifications for codec_specific_data by Ralph Giles and me Modified: trunk/DOCS/tech/nut.txt ============================================================================== --- trunk/DOCS/tech/nut.txt (original) +++ trunk/DOCS/tech/nut.txt Sat Nov 25 12:28:38 2006 @@ -575,6 +575,12 @@ to generate any specific decoded samples the encoder name and version, shall be considered essential as it is very usefull to workaround possible encoder bugs + The global headers MUST consist of the normal + sequence of header packets required for codec initialization, in the + order defined in the codec spec. An implementation MAY strip metadata and + other redundant information not necessary for correct playback from the + global headers as long as no incorrect values are stored and as long as + the striped result is not less valid per codec spec as before striping frame_code (f(8)) frame_code is an 8-bit field which exists before every frame, it can

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[nut]: r266 - trunk/libnut/libnut.h
by ods15 25 Nov '06

25 Nov '06

Author: ods15 Date: Sat Nov 25 07:24:04 2006 New Revision: 266 Modified: trunk/libnut/libnut.h Log: some doxygen fixes Modified: trunk/libnut/libnut.h ============================================================================== --- trunk/libnut/libnut.h (original) +++ trunk/libnut/libnut.h Sat Nov 25 07:24:04 2006 @@ -28,23 +28,20 @@ typedef struct nut_context_s nut_context_t; -/// \ingroup demuxer muxer -/// @{ - -/// Memory allocation function pointers +/// Memory allocation function pointers \ingroup demuxer muxer typedef struct { void * (*malloc)(size_t size); ///< Memory allocation malloc function pointer void * (*realloc)(void *ptr, size_t size); ///< Memory allocation realloc function pointer void (*free)(void *ptr); ///< Memory allocation free function pointer } nut_alloc_t; -/// Timebase struct +/// Timebase struct \ingroup demuxer muxer typedef struct { int nom; ///< Example: 1001 int den; ///< Example: 24000 } nut_timebase_t; -/// Stream header struct +/// Stream header struct \ingroup demuxer muxer typedef struct { int type; ///< Possible values are enum ::nut_stream_class_t. Value of -1 terminates a stream header array int fourcc_len; ///< Length of fourcc @@ -63,17 +60,18 @@ int sample_width; ///< Ratio to stretch the video. May only be zero if #sample_height is zero int sample_height; ///< Ratio to stretch the video. May only be zero if #sample_width is zero int colorspace_type; - /// @} + /// @} /// \name audio /// Only used is type is #NUT_AUDIO_CLASS @{ int samplerate_nom; ///< Sample rate of audio. Example: 44100 int samplerate_denom; ///< Sample rate denominator of audio. Example: 1 int channel_count; ///< Amount of audio channels + /// @} } nut_stream_header_t; -/// Single info field struct +/// Single info field struct \ingroup demuxer muxer typedef struct { char type[7]; ///< NULL-terminated string char name[65]; ///< NULL-terminated string. Name of info field @@ -83,7 +81,7 @@ uint8_t * data; ///< Used if #type is non-numeric } nut_info_field_t; -/// Single info packet struct +/// Single info packet struct \ingroup demuxer muxer typedef struct { int count; ///< Indicates how many info fields are provided in #fields int stream_id_plus1; ///< Zero indicates non-stream-specific info packet @@ -94,7 +92,7 @@ nut_info_field_t * fields; ///< Info fields, has #count elements } nut_info_packet_t; -/// Single frame packet struct +/// Single frame packet struct \ingroup demuxer muxer typedef struct { int len; ///< Length of frame in bytes. \b Must be zero if #NUT_FLAG_EOR is set. int stream; ///< Stream index of frame @@ -102,7 +100,6 @@ int flags; ///< Frame flags from #nut_frame_flags_t int64_t next_pts; ///< Only used in muxer. Only necessary if nut_write_frame_reorder() is used. } nut_packet_t; -/// @} @@ -303,7 +300,7 @@ * - "s" - Integer value * - "r" - Numerator of fraction * - "t" - Integer timestamp in timebase #tb - * - Other: Length of #data in bytes + * - Other - Length of #data in bytes * * In the case of UTF-8 string, length of #data \b must \b not contain the * terminating NUL (U+0000).

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r21189 - trunk/DOCS/tech/nut.txt
by michael 25 Nov '06

25 Nov '06

Author: michael Date: Fri Nov 24 13:51:33 2006 New Revision: 21189 Modified: trunk/DOCS/tech/nut.txt Log: codec_specific_data clarification if anyone disagrees or has suggestions to improve it then shout Modified: trunk/DOCS/tech/nut.txt ============================================================================== --- trunk/DOCS/tech/nut.txt (original) +++ trunk/DOCS/tech/nut.txt Fri Nov 24 13:51:33 2006 @@ -568,6 +568,13 @@ the exact format is specified in the codec spec for H.264 the NAL units MUST be formatted as in a bytestream (with 00 00 01 prefixes) + codec_specific_data SHOULD contain exactly the essential global packets + needed to decode a stream, more specifically it SHOULD NOT contain packets + which contain only non essential metadata like author, title, ... + it also MUST NOT contain normal packets which cause the reference decoder + to generate any specific decoded samples + the encoder name and version, shall be considered essential as it is very + usefull to workaround possible encoder bugs frame_code frame_code is an 8-bit field which exists before every frame, it can

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