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mp4_clipper: align start offset to keyframe #1538

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mp4_clipper: align start offset to keyframe #1538

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8 changes: 8 additions & 0 deletions ngx_http_vod_module.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1539,6 +1539,14 @@ ngx_http_vod_init_parse_params_metadata(
parse_params->parse_type |= ctx->submodule_context.conf->parse_flags;
parse_params->codecs_mask = request->codecs_mask;
}
else
{
parse_params->parse_type = 0;
if (ctx->submodule_context.conf->segmenter.align_to_key_frames)
{
parse_params->parse_type |= PARSE_FLAG_ALIGN_TO_KEYFRAME;
}
}

request_tracks_mask = ctx->submodule_context.request_params.tracks_mask;
if (ctx->submodule_context.request_params.sequence_tracks_mask != NULL)
Expand Down
2 changes: 2 additions & 0 deletions vod/media_format.h
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,8 @@
#define PARSE_FLAG_INITIAL_PTS_DELAY (0x01000000)
#define PARSE_FLAG_KEY_FRAME_BITRATE (0x02000000)

#define PARSE_FLAG_ALIGN_TO_KEYFRAME (0x10000000)

// flag groups
#define PARSE_FLAG_FRAMES_ALL (PARSE_FLAG_FRAMES_DURATION | PARSE_FLAG_FRAMES_PTS_DELAY | PARSE_FLAG_FRAMES_SIZE | PARSE_FLAG_FRAMES_OFFSET | PARSE_FLAG_FRAMES_IS_KEY)
#define PARSE_FLAG_FRAMES_ALL_EXCEPT_OFFSETS (PARSE_FLAG_FRAMES_DURATION | PARSE_FLAG_FRAMES_PTS_DELAY | PARSE_FLAG_FRAMES_SIZE | PARSE_FLAG_FRAMES_IS_KEY)
Expand Down
139 changes: 138 additions & 1 deletion vod/mp4/mp4_clipper.c
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Original file line number Diff line number Diff line change
Expand Up @@ -93,6 +93,7 @@ enum {
MP4_CLIPPER_TRAK_INDEX_STSZ_DATA,
MP4_CLIPPER_TRAK_INDEX_STCO_HEADER,
MP4_CLIPPER_TRAK_INDEX_STCO_DATA,
MP4_CLIPPER_TRAK_INDEX_EDTS_ATOM,

MP4_CLIPPER_TRAK_INDEX_COUNT
};
Expand Down Expand Up @@ -126,6 +127,7 @@ typedef struct {
size_t data_size;
size_t atom_size;
uint32_t entries;
uint64_t prefix;
} stts_clip_result_t;

typedef struct {
Expand Down Expand Up @@ -197,6 +199,7 @@ typedef struct {
size_t stbl_atom_size;
size_t minf_atom_size;
size_t mdia_atom_size;
size_t edts_atom_size;
size_t trak_atom_size;
} parsed_trak_t;

Expand Down Expand Up @@ -530,10 +533,91 @@ mp4_clipper_mdhd_update_atom(u_char* p, mdhd_clip_result_t* mdhd)
}

// stts
static vod_status_t
mp4_clipper_stts_seek_to_keyframe(
parse_trak_atom_context_t* context,
stts_iterator_state_t* iterator,
atom_info_t* stss_atom,
uint64_t* prefix)
{
vod_status_t rc;
uint32_t* first_entry;
uint32_t* entry;
uint64_t initial_duration;
uint32_t sample_duration;
uint32_t sample_count;
uint32_t entry_index;
uint32_t key_index;
uint32_t entries;
uint32_t count;
uint32_t left;

if (stss_atom->size <= 0)
{
return VOD_OK;
}

rc = mp4_parser_validate_stss_atom(context->request_context, stss_atom, &entries);
if (rc != VOD_OK)
{
return rc;
}

if (entries <= 0)
{
vod_log_error(VOD_LOG_ERR, context->request_context->log, 0,
"mp4_clipper_stts_seek_to_keyframe: zero entries");
return VOD_BAD_DATA;
}

// first the last key frame before iterator->frame_index
first_entry = (uint32_t*)(stss_atom->ptr + sizeof(stss_atom_t));
entry_index = mp4_parser_find_stss_entry(iterator->frame_index, first_entry, entries);
entry = first_entry + entry_index;
if (entry_index > 0 && (entry_index >= entries || parse_be32(entry) > iterator->frame_index + 1))
{
entry--;
}

key_index = parse_be32(entry) - 1;

// seek back to key_index
initial_duration = iterator->accum_duration;
sample_count = parse_be32(iterator->cur_entry->count);
while (iterator->frame_index > key_index)
{
if (iterator->sample_count >= sample_count)
{
iterator->cur_entry--;
iterator->sample_count = 0;
sample_count = parse_be32(iterator->cur_entry->count);
continue;
}

count = sample_count - iterator->sample_count;
left = iterator->frame_index - key_index;
if (count > left)
{
count = left;
}

sample_duration = parse_be32(iterator->cur_entry->duration);

iterator->sample_count += count;
iterator->frame_index -= count;
iterator->accum_duration -= count * sample_duration;
}

*prefix = initial_duration - iterator->accum_duration;

return VOD_OK;
}

static vod_status_t
mp4_clipper_stts_clip_data(
parse_trak_atom_context_t* context,
atom_info_t* atom_info,
atom_info_t* stss_atom,
stts_clip_result_t* result,
uint32_t* first_frame,
uint32_t* last_frame)
Expand Down Expand Up @@ -574,6 +658,15 @@ mp4_clipper_stts_clip_data(
"mp4_clipper_stts_clip_data: clip from longer than video duration");
return VOD_BAD_REQUEST;
}

if (context->parse_params.parse_type & PARSE_FLAG_ALIGN_TO_KEYFRAME)
{
rc = mp4_clipper_stts_seek_to_keyframe(context, &iterator, stss_atom, &result->prefix);
if (rc != VOD_OK)
{
return rc;
}
}
}

result->first_entry = iterator.cur_entry;
Expand All @@ -584,7 +677,8 @@ mp4_clipper_stts_clip_data(
{
// Note: the below was done to match nginx mp4, may be better to do
// clip_to = (((uint64_t)context->parse_params.clip_to * context->timescale) / 1000);
clip_to = iterator.accum_duration + (((uint64_t)(context->parse_params.clip_to - context->parse_params.clip_from) * context->timescale) / 1000);
clip_to = iterator.accum_duration + result->prefix +
(((uint64_t)(context->parse_params.clip_to - context->parse_params.clip_from) * context->timescale) / 1000);
}
else
{
Expand Down Expand Up @@ -1538,6 +1632,7 @@ mp4_clipper_process_moov_atom_callback(void* ctx, atom_info_t* atom_info)
rc = mp4_clipper_stts_clip_data(
&parse_context,
&parsed_trak->atoms[TRAK_ATOM_STTS],
&parsed_trak->atoms[TRAK_ATOM_STSS],
&parsed_trak->stts,
&parse_context.first_frame,
&parse_context.last_frame);
Expand All @@ -1546,6 +1641,8 @@ mp4_clipper_process_moov_atom_callback(void* ctx, atom_info_t* atom_info)
return rc;
}

parsed_trak->mdhd.duration += parsed_trak->stts.prefix;

if (parse_context.first_frame >= parse_context.last_frame)
{
return VOD_OK;
Expand Down Expand Up @@ -1628,8 +1725,15 @@ mp4_clipper_process_moov_atom_callback(void* ctx, atom_info_t* atom_info)
full_atom_size(parsed_trak->atoms[TRAK_ATOM_HDLR]) +
parsed_trak->minf_atom_size;

if (parsed_trak->stts.prefix > 0)
{
parsed_trak->edts_atom_size = 2 * ATOM_HEADER_SIZE + sizeof(elst_atom_t) + sizeof(elst64_entry_t);
context->result.alloc_size += parsed_trak->edts_atom_size;
}

parsed_trak->trak_atom_size = ATOM_HEADER_SIZE +
full_atom_size(parsed_trak->atoms[TRAK_ATOM_TKHD]) +
parsed_trak->edts_atom_size +
parsed_trak->mdia_atom_size;

context->result.moov_atom_size += parsed_trak->trak_atom_size;
Expand All @@ -1649,6 +1753,26 @@ mp4_clipper_process_moov_atom_callback(void* ctx, atom_info_t* atom_info)
return VOD_OK;
}

static u_char*
mp4_clipper_edts_write_atom(u_char* p, parsed_trak_t* parsed_trak)
{
size_t elst_atom_size;

elst_atom_size = parsed_trak->edts_atom_size - ATOM_HEADER_SIZE;

write_atom_header(p, parsed_trak->edts_atom_size, 'e', 'd', 't', 's');
write_atom_header(p, elst_atom_size, 'e', 'l', 's', 't');

write_be32(p, 1 << 24); // version = 1
write_be32(p, 1); // entries
write_be64(p, parsed_trak->tkhd.duration);
write_be64(p, parsed_trak->stts.prefix);
write_be16(p, 1); // media_rate
write_be16(p, 0); // reserved

return p;
}

static u_char*
mp4_clipper_trak_write_atom(u_char* p, void* write_context, parsed_trak_t* parsed_trak, bool_t copy_data, int64_t chunk_pos_diff)
{
Expand All @@ -1657,6 +1781,12 @@ mp4_clipper_trak_write_atom(u_char* p, void* write_context, parsed_trak_t* parse
write_atom_header(p, parsed_trak->trak_atom_size, 't', 'r', 'a', 'k');
copy_full_atom(p, parsed_trak->atoms[TRAK_ATOM_TKHD]);
mp4_clipper_tkhd_update_atom(p - parsed_trak->atoms[TRAK_ATOM_TKHD].size, &parsed_trak->tkhd);

if (parsed_trak->edts_atom_size > 0)
{
p = mp4_clipper_edts_write_atom(p, parsed_trak);
}

write_atom_header(p, parsed_trak->mdia_atom_size, 'm', 'd', 'i', 'a');
copy_full_atom(p, parsed_trak->atoms[TRAK_ATOM_MDHD]);
mp4_clipper_mdhd_update_atom(p - parsed_trak->atoms[TRAK_ATOM_MDHD].size, &parsed_trak->mdhd);
Expand All @@ -1678,6 +1808,13 @@ mp4_clipper_trak_write_atom(u_char* p, void* write_context, parsed_trak_t* parse
mp4_clipper_tkhd_update_atom((u_char*)parsed_trak->atoms[TRAK_ATOM_TKHD].ptr, &parsed_trak->tkhd);
write_full_atom(write_context, MP4_CLIPPER_TRAK_INDEX_TKHD_ATOM, parsed_trak->atoms[TRAK_ATOM_TKHD]);

if (parsed_trak->edts_atom_size > 0)
{
// trak.edts
p = mp4_clipper_edts_write_atom(p, parsed_trak);
mp4_clipper_write_tail(write_context, MP4_CLIPPER_TRAK_INDEX_EDTS_ATOM, p - parsed_trak->edts_atom_size, parsed_trak->edts_atom_size);
}

// trak.mdia
write_atom_header(p, parsed_trak->mdia_atom_size, 'm', 'd', 'i', 'a');
mp4_clipper_write_tail(write_context, MP4_CLIPPER_TRAK_INDEX_MDIA_HEADER, p - ATOM_HEADER_SIZE, ATOM_HEADER_SIZE);
Expand Down
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